Discussion:
sort of OT - car Aircon
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TimW
2024-06-10 13:23:42 UTC
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The modern world being what it is the latest old banger I am driving has
Air Conditioning - except that it hasn't worked since I have had it.
That wouldn't be a problem, I could wind down the window but the heating
doesn't work either and it was cold driving in the Winter. I wondered if
I needed to bleed air out of the pipes to the heater and turned what
looked like a bleed screw but then realised that gas was escaping and I
was further de-gassing the aircon.

Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon fixed
might I expect the heating to work? Car is a Mitsubishi Colt.

Tim W
alan_m
2024-06-10 13:37:47 UTC
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Post by TimW
The modern world being what it is the latest old banger I am driving has
Air Conditioning - except that it hasn't worked since I have had it.
That wouldn't be a problem, I could wind down the window but the heating
doesn't work either and it was cold driving in the Winter. I wondered if
I needed to bleed air out of the pipes to the heater and turned what
looked like a bleed screw but then realised that gas was escaping and I
was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon fixed
might I expect the heating to work? Car is a Mitsubishi Colt.
Tim W
Is the blower motor working? If it appears not to work at the lower
settings does it actually still work on the highest setting.
--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk
TimW
2024-06-10 14:08:26 UTC
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Post by alan_m
Post by TimW
The modern world being what it is the latest old banger I am driving
has Air Conditioning - except that it hasn't worked since I have had
it. That wouldn't be a problem, I could wind down the window but the
heating doesn't work either and it was cold driving in the Winter. I
wondered if I needed to bleed air out of the pipes to the heater and
turned what looked like a bleed screw but then realised that gas was
escaping and I was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon
fixed might I expect the heating to work? Car is a Mitsubishi Colt.
Tim W
Is the blower motor working? If it appears not to work at the lower
settings does it actually still work on the highest setting.
The fan works, but it blows neither hot nor cold, just air at air temp.
TW
Brian
2024-06-10 18:53:42 UTC
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Post by TimW
Post by alan_m
Post by TimW
The modern world being what it is the latest old banger I am driving
has Air Conditioning - except that it hasn't worked since I have had
it. That wouldn't be a problem, I could wind down the window but the
heating doesn't work either and it was cold driving in the Winter. I
wondered if I needed to bleed air out of the pipes to the heater and
turned what looked like a bleed screw but then realised that gas was
escaping and I was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon
fixed might I expect the heating to work? Car is a Mitsubishi Colt.
Tim W
Is the blower motor working? If it appears not to work at the lower
settings does it actually still work on the highest setting.
The fan works, but it blows neither hot nor cold, just air at air temp.
TW
Sounds like the ‘flaps’ which direct the air in path required aren’t
moving.

In older cars, these are linked to the controls via levers and mechanical
cable links. In modern ones, switches and motors do the job.
Andrew
2024-06-11 10:42:25 UTC
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Post by Brian
Post by TimW
Post by alan_m
Post by TimW
The modern world being what it is the latest old banger I am driving
has Air Conditioning - except that it hasn't worked since I have had
it. That wouldn't be a problem, I could wind down the window but the
heating doesn't work either and it was cold driving in the Winter. I
wondered if I needed to bleed air out of the pipes to the heater and
turned what looked like a bleed screw but then realised that gas was
escaping and I was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon
fixed might I expect the heating to work? Car is a Mitsubishi Colt.
Tim W
Is the blower motor working? If it appears not to work at the lower
settings does it actually still work on the highest setting.
The fan works, but it blows neither hot nor cold, just air at air temp.
TW
Sounds like the ‘flaps’ which direct the air in path required aren’t
moving.
In older cars, these are linked to the controls via levers and mechanical
cable links. In modern ones, switches and motors do the job.
What happens when the OP presses the air-recirculation button ?.
This must have an electro-magnetic connection to a flap somewhere
and it should be possible to hear this.
nibble
2024-06-10 13:44:42 UTC
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Post by TimW
The modern world being what it is the latest old banger I am driving has
Air Conditioning - except that it hasn't worked since I have had it.
That wouldn't be a problem, I could wind down the window but the heating
doesn't work either and it was cold driving in the Winter. I wondered if
I needed to bleed air out of the pipes to the heater and turned what
looked like a bleed screw but then realised that gas was escaping and I
was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon fixed
might I expect the heating to work? Car is a Mitsubishi Colt.
Tim W
Two obvious questions:

1) When you say they both don't work, is there still a blast of air
coming out that is neither heated or cooled, or no air coming out at all?

2) Does the car's temperature gauge get up to normal after a few miles
of driving?

nib
TimW
2024-06-10 14:10:07 UTC
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Post by nibble
Post by TimW
The modern world being what it is the latest old banger I am driving
has Air Conditioning - except that it hasn't worked since I have had
it. That wouldn't be a problem, I could wind down the window but the
heating doesn't work either and it was cold driving in the Winter. I
wondered if I needed to bleed air out of the pipes to the heater and
turned what looked like a bleed screw but then realised that gas was
escaping and I was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon
fixed might I expect the heating to work? Car is a Mitsubishi Colt.
Tim W
1) When you say they both don't work, is there still a blast of air
coming out that is neither heated or cooled, or no air coming out at all?
2) Does the car's temperature gauge get up to normal after a few miles
of driving?
nib
The fan works. There is no temperature gauge, only an overheating light
which doesn't come on.

Tim W
Harry Bloomfield Esq
2024-06-10 18:31:58 UTC
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Post by TimW
The fan works. There is no temperature gauge, only an overheating light
which doesn't come on.
Feel the top hose, on the radiator, after a decent run - is it hot?
Andrew
2024-06-11 10:47:48 UTC
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Post by Harry Bloomfield Esq
Post by TimW
The fan works. There is no temperature gauge, only an overheating
light which doesn't come on.
Feel the top hose, on the radiator, after a decent run - is it hot?
THis being uk.d-i-y, doesn't everyone have a hand-held laser temperature
measuring device ?.

The two pipes that supply the heater should be easy to identify
at the back of the engine bay, going through the bulkhead, but
I seem to recollect that on my 1998 Astra F, there was also a
temperature-controlled valve that turned this loop off when the
temp was above a certian level, presumably because you didn't
need hot water circulating into the heater block when the heater
was not required.

Something else to check for
alan_m
2024-06-11 11:13:58 UTC
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Post by Andrew
Post by Harry Bloomfield Esq
Post by TimW
The fan works. There is no temperature gauge, only an overheating
light which doesn't come on.
Feel the top hose, on the radiator, after a decent run - is it hot?
THis being uk.d-i-y, doesn't everyone have a hand-held laser temperature
measuring device ?.
The two pipes that supply the heater should be easy to identify
at the back of the engine bay, going through the bulkhead, but
I seem to recollect that on my 1998 Astra F, there was also a
temperature-controlled valve that turned this loop off when the
temp was above a certian level, presumably because you didn't
need hot water circulating into the heater block when the heater
was not required.
Something else to check for
Also, on modern ICE vehicles the circulation to the heater matrix
(radiator) may be delayed until engine has reached its full operating
temperature.
--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk
Davey
2024-06-11 11:16:21 UTC
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On Tue, 11 Jun 2024 11:47:48 +0100
Post by Andrew
THis being uk.d-i-y, doesn't everyone have a hand-held laser
temperature measuring device ?.
No.
--
Davey.
Andrew
2024-06-11 12:14:34 UTC
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Post by Davey
On Tue, 11 Jun 2024 11:47:48 +0100
Post by Andrew
THis being uk.d-i-y, doesn't everyone have a hand-held laser
temperature measuring device ?.
No.
Do you have a cat ?.

Lots of fun getting mog to chase the red spot around the
wall.

Also handy for measuring temperatures :-)
Davey
2024-06-11 13:15:53 UTC
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On Tue, 11 Jun 2024 13:14:34 +0100
Post by Andrew
Post by Davey
On Tue, 11 Jun 2024 11:47:48 +0100
Post by Andrew
THis being uk.d-i-y, doesn't everyone have a hand-held laser
temperature measuring device ?.
No.
Do you have a cat ?.
Lots of fun getting mog to chase the red spot around the
wall.
Also handy for measuring temperatures :-)
I have a laser distance measuring device, and the visiting cats
(all outdoors) could chase that around, I suppose. I have no cats of my
own.
But as for temperature, I rely on a contact thermocouple that plugs
into my DMM and gives a readout.
We once met a dog-owner at San Francisco's Fisherman's Wharf, whose dog
chased a laser pointer. He had even appeared on TV on The Dave
Letterman Show, as this was unusual at the time, for dogs to do it.
Times change.
--
Davey.
Harry Bloomfield Esq
2024-06-11 18:37:32 UTC
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Post by Davey
We once met a dog-owner at San Francisco's Fisherman's Wharf, whose dog
chased a laser pointer. He had even appeared on TV on The Dave
Letterman Show, as this was unusual at the time, for dogs to do it.
Border collies here, and almost all will chase a laser spot, or in fact
any moving bright spot.
Jeff Layman
2024-06-10 13:51:00 UTC
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Post by TimW
The modern world being what it is the latest old banger I am driving has
Air Conditioning - except that it hasn't worked since I have had it.
That wouldn't be a problem, I could wind down the window but the heating
doesn't work either and it was cold driving in the Winter. I wondered if
I needed to bleed air out of the pipes to the heater and turned what
looked like a bleed screw but then realised that gas was escaping and I
was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon fixed
might I expect the heating to work? Car is a Mitsubishi Colt.
I've always understood that the heating and aircon were independent. You
can have the aircon on full and the heating on full at the same time -
the aircon just removes water from the incoming air before the heater
warms it up. It's the way to get the screen demisted in winter before
the engine has warmed up enough to heat the air.

BICBW. Perhaps cars with climate control do it a different way.
--
Jeff
Theo
2024-06-10 14:06:13 UTC
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Post by Jeff Layman
Post by TimW
The modern world being what it is the latest old banger I am driving has
Air Conditioning - except that it hasn't worked since I have had it.
That wouldn't be a problem, I could wind down the window but the heating
doesn't work either and it was cold driving in the Winter. I wondered if
I needed to bleed air out of the pipes to the heater and turned what
looked like a bleed screw but then realised that gas was escaping and I
was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon fixed
might I expect the heating to work? Car is a Mitsubishi Colt.
I've always understood that the heating and aircon were independent. You
can have the aircon on full and the heating on full at the same time -
the aircon just removes water from the incoming air before the heater
warms it up. It's the way to get the screen demisted in winter before
the engine has warmed up enough to heat the air.
BICBW. Perhaps cars with climate control do it a different way.
They're normally separate: heater uses cooling water from the engine, aircon
uses refrigerant with a compressor. They come together in the dash - air
gets blown over a heater matrix (heat exchanger) and the aircon evaporator.

Climate control may lock them out so you don't run both together, but the
systems are both there, you just can't open both concurrently. You have a
single temperature knob rather than a flap to open the heater matrix and a
button to connect the aircon compressor clutch to the engine belt and it
controls which is enabled when.

On EVs it's either the same arrangement with a resistive heater instead of
using engine coolant, or they use the aircon in reverse as a heat pump.

Theo
TimW
2024-06-10 14:12:41 UTC
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Post by Theo
Post by Jeff Layman
Post by TimW
The modern world being what it is the latest old banger I am driving has
Air Conditioning - except that it hasn't worked since I have had it.
That wouldn't be a problem, I could wind down the window but the heating
doesn't work either and it was cold driving in the Winter. I wondered if
I needed to bleed air out of the pipes to the heater and turned what
looked like a bleed screw but then realised that gas was escaping and I
was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon fixed
might I expect the heating to work? Car is a Mitsubishi Colt.
I've always understood that the heating and aircon were independent. You
can have the aircon on full and the heating on full at the same time -
the aircon just removes water from the incoming air before the heater
warms it up. It's the way to get the screen demisted in winter before
the engine has warmed up enough to heat the air.
BICBW. Perhaps cars with climate control do it a different way.
They're normally separate: heater uses cooling water from the engine, aircon
uses refrigerant with a compressor. They come together in the dash - air
gets blown over a heater matrix (heat exchanger) and the aircon evaporator.
Climate control may lock them out so you don't run both together, but the
systems are both there, you just can't open both concurrently. You have a
single temperature knob rather than a flap to open the heater matrix and a
button to connect the aircon compressor clutch to the engine belt and it
controls which is enabled when.
On EVs it's either the same arrangement with a resistive heater instead of
using engine coolant, or they use the aircon in reverse as a heat pump.
Theo
Yes. that's what I thought. But wondered if possibly they came together
elsewhere on this motor, eg one set of pipes to the dash only.
TW
The Natural Philosopher
2024-06-12 11:16:56 UTC
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Post by Theo
They're normally separate: heater uses cooling water from the engine, aircon
uses refrigerant with a compressor. They come together in the dash - air
gets blown over a heater matrix (heat exchanger) and the aircon evaporator.
Climate control may lock them out so you don't run both together,
The reverse Climate control ensures that you can run them together -
vital for winter demisting.
--
"If you don’t read the news paper, you are un-informed. If you read the
news paper, you are mis-informed."

Mark Twain
The Natural Philosopher
2024-06-12 11:17:15 UTC
Reply
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Post by Theo
They're normally separate: heater uses cooling water from the engine, aircon
uses refrigerant with a compressor. They come together in the dash - air
gets blown over a heater matrix (heat exchanger) and the aircon evaporator.
Climate control may lock them out so you don't run both together,
The reverse Climate control ensures that you can run them together -
vital for winter demisting.
--
"If you don’t read the news paper, you are un-informed. If you read the
news paper, you are mis-informed."

Mark Twain
Silent Ice
2024-06-10 14:38:25 UTC
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Post by TimW
The modern world being what it is the latest old banger I am driving has
Air Conditioning - except that it hasn't worked since I have had it.
That wouldn't be a problem, I could wind down the window but the heating
doesn't work either and it was cold driving in the Winter. I wondered if
I needed to bleed air out of the pipes to the heater and turned what
looked like a bleed screw but then realised that gas was escaping and I
was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon fixed
might I expect the heating to work? Car is a Mitsubishi Colt.
Tim W
I have the same understanding as Theo.

The aircon is normally powered via a compressor that likely runs off the
alt belt. Might be as simple as a fuse.. Depending how long it's been it
might need a regas, but if the compressor is bust or the lines have
corroded over time then that might not be an economical fix, as I found
out on my last car.

The heater element is separate and heated by the engine's cooling
system. Air from the blower is diverted across the matrix and as the
engine warms up it warms the air. I think I'm right in saying that the
coolant always circulates across this matrix but when the engine
thermostat opens at around 90degrees it also flows into the radiator at
the front of the car. If the blower works but there's no heat even when
the engine is up to temp it suggests a blockage. You might be able to
clear it with a coolant flush. When was the coolant last changed?



As you don't have cold or hot, it could also be the diverter that
redirects the air across the relevant matrix is broken. Depending on the
age and spec of car they will be either mechanical or motorised.
nibble
2024-06-10 16:22:40 UTC
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Post by Silent Ice
Post by TimW
The modern world being what it is the latest old banger I am driving
has Air Conditioning - except that it hasn't worked since I have had
it. That wouldn't be a problem, I could wind down the window but the
heating doesn't work either and it was cold driving in the Winter. I
wondered if I needed to bleed air out of the pipes to the heater and
turned what looked like a bleed screw but then realised that gas was
escaping and I was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon
fixed might I expect the heating to work? Car is a Mitsubishi Colt.
Tim W
I have the same understanding as Theo.
The aircon is normally powered via a compressor that likely runs off the
alt belt. Might be as simple as a fuse.. Depending how long it's been it
might need a regas, but if the compressor is bust or the lines have
corroded over time then that might not be an economical fix, as I found
out on my last car.
The heater element is separate and heated by the engine's cooling
system. Air from the blower is diverted across the matrix and as the
engine warms up it warms the air. I think I'm right in saying that the
coolant always circulates across this matrix but when the engine
thermostat opens at around 90degrees it also flows into the radiator at
the front of the car. If the blower works but there's no heat even when
the engine is up to temp it suggests a blockage. You might be able to
clear it with a coolant flush. When was the coolant last changed?
http://youtu.be/M9SIafVsqyc
As you don't have cold or hot, it could also be the diverter that
redirects the air across the relevant matrix is broken. Depending on the
age and spec of car they will be either mechanical or motorised.
From my playing and experience, the two most likely reasons for air-con
not working are broken drive belt on the compressor or gas all leaked
out. Maybe also an electrical fault on the clutch that takes it in or
out of service.

The two most likely reasons for heating not working are a stuck flap
controlling whether the air goes via the heater matrix or not (had that
on a Citroen ZX) or engine not getting up to temperature, such as a
stuck-open thermostat (had that on a Mazda 323).

There's not much that affects both.

I don't think there's always air diversion around the air-con
evaporator, it behaves as it it's always in flow and if you don't want
full air-con you either have a 2-speed compressor (like my Smart) or you
just blend in some hot air from the heater.

Most likely two separate faults?

nib
charles
2024-06-10 18:08:03 UTC
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Post by nibble
Post by Silent Ice
Post by TimW
The modern world being what it is the latest old banger I am driving
has Air Conditioning - except that it hasn't worked since I have had
it. That wouldn't be a problem, I could wind down the window but the
heating doesn't work either and it was cold driving in the Winter. I
wondered if I needed to bleed air out of the pipes to the heater and
turned what looked like a bleed screw but then realised that gas was
escaping and I was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon
fixed might I expect the heating to work? Car is a Mitsubishi Colt.
Tim W
I have the same understanding as Theo.
The aircon is normally powered via a compressor that likely runs off
the alt belt. Might be as simple as a fuse.. Depending how long it's
been it might need a regas, but if the compressor is bust or the lines
have corroded over time then that might not be an economical fix, as I
found out on my last car.
The heater element is separate and heated by the engine's cooling
system. Air from the blower is diverted across the matrix and as the
engine warms up it warms the air. I think I'm right in saying that the
coolant always circulates across this matrix but when the engine
thermostat opens at around 90degrees it also flows into the radiator at
the front of the car. If the blower works but there's no heat even
when the engine is up to temp it suggests a blockage. You might be
able to clear it with a coolant flush. When was the coolant last
changed? http://youtu.be/M9SIafVsqyc
As you don't have cold or hot, it could also be the diverter that
redirects the air across the relevant matrix is broken. Depending on
the age and spec of car they will be either mechanical or motorised.
From my playing and experience, the two most likely reasons for air-con
not working are broken drive belt on the compressor or gas all leaked
out. Maybe also an electrical fault on the clutch that takes it in or
out of service.
The two most likely reasons for heating not working are a stuck flap
controlling whether the air goes via the heater matrix or not (had that
on a Citroen ZX) or engine not getting up to temperature, such as a
stuck-open thermostat (had that on a Mazda 323).
and a blocked heater matrix. I had that on my Cortina IV.
--
from KT24 in Surrey, England - sent from my RISC OS 4té²
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle
Jim the Geordie
2024-06-10 15:53:30 UTC
Reply
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Post by TimW
The modern world being what it is the latest old banger I am driving has
Air Conditioning - except that it hasn't worked since I have had it.
That wouldn't be a problem, I could wind down the window but the heating
doesn't work either and it was cold driving in the Winter. I wondered if
I needed to bleed air out of the pipes to the heater and turned what
looked like a bleed screw but then realised that gas was escaping and I
was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon fixed
might I expect the heating to work? Car is a Mitsubishi Colt.
Tim W
My, then 14yo, Mitsubishi Space Star needed regassing.
Local garage did it. Cost ~£35 a couple of years ago.
Worked perfectly until I sold it when it was 19yo.
May be going still.
--
Jim the Geordie
John Rumm
2024-06-11 12:57:56 UTC
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Post by TimW
The modern world being what it is the latest old banger I am driving has
Air Conditioning - except that it hasn't worked since I have had it.
That wouldn't be a problem, I could wind down the window but the heating
doesn't work either and it was cold driving in the Winter. I wondered if
I needed to bleed air out of the pipes to the heater and turned what
looked like a bleed screw but then realised that gas was escaping and I
was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon fixed
might I expect the heating to work? Car is a Mitsubishi Colt.
It sounds like you probably have more than one issue...

Assuming that the heater part is "conventional" then there should be a
hot water feed and return to the heater matrix. This is what should heat
the air (either ram fed or fan fed) into the cabin. It is not unknown
for the heater matrix to be "bypassed" if it springs a leak (since they
are often well embedded in the dash and can be a PITA to replace). Also
check there is enough water in the radiator. On some cars there may be
additional valves / stats to inhibit flow through the matrix until the
engine is up to temp.

After the heater matrix, the air should pass through the aircon heat
exchanger. When the aircon is switched on you should hear / see some
activity as the compressor belt is engaged. (some systems also have a
sight glass where you can see if the cooling gas/ liquid is being
circulated). If working normally it will automatically cut in and out as
it maintains the required level of cooling. If the gas level is low, it
may run continuously and not actually cool much or at all. If the gas
level is *very* low it may not even fire up at all. The fix for both it
to get it re-gassed. They will normally assess if for leaks at the same
time, and add the right amount of lubricant to the gas as well.
--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/
Jeff Layman
2024-06-11 14:13:16 UTC
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Post by John Rumm
Post by TimW
The modern world being what it is the latest old banger I am driving has
Air Conditioning - except that it hasn't worked since I have had it.
That wouldn't be a problem, I could wind down the window but the heating
doesn't work either and it was cold driving in the Winter. I wondered if
I needed to bleed air out of the pipes to the heater and turned what
looked like a bleed screw but then realised that gas was escaping and I
was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon fixed
might I expect the heating to work? Car is a Mitsubishi Colt.
It sounds like you probably have more than one issue...
It does - and more expense!
Post by John Rumm
Assuming that the heater part is "conventional" then there should be a
hot water feed and return to the heater matrix. This is what should heat
the air (either ram fed or fan fed) into the cabin. It is not unknown
for the heater matrix to be "bypassed" if it springs a leak (since they
are often well embedded in the dash and can be a PITA to replace). Also
check there is enough water in the radiator. On some cars there may be
additional valves / stats to inhibit flow through the matrix until the
engine is up to temp.
After the heater matrix, the air should pass through the aircon heat
exchanger.
Are you sure that the the air passes the aircon heat exchanger /after/
the heater matrix? If you're trying to stop humid air reaching the
screen you should remove it by condensing it out with the aircon heat
exchanger whilst it's still cold. Once the water content has been
reduced it doesn't matter if you use the heater to warm the dried air,
as even if that air hits the cold screen it won't have water in it to
mist up the screen. If you try to do it the other way round, it's much
more difficult.

When the aircon is switched on you should hear / see some
Post by John Rumm
activity as the compressor belt is engaged. (some systems also have a
sight glass where you can see if the cooling gas/ liquid is being
circulated). If working normally it will automatically cut in and out as
it maintains the required level of cooling. If the gas level is low, it
may run continuously and not actually cool much or at all. If the gas
level is *very* low it may not even fire up at all. The fix for both it
to get it re-gassed. They will normally assess if for leaks at the same
time, and add the right amount of lubricant to the gas as well.
If it's an old car I wonder what refrigerant will be used to regas it.
--
Jeff
Davey
2024-06-11 16:25:48 UTC
Reply
Permalink
On Tue, 11 Jun 2024 15:13:16 +0100
Post by Jeff Layman
Post by John Rumm
After the heater matrix, the air should pass through the aircon heat
exchanger.
Are you sure that the the air passes the aircon heat
exchanger /after/ the heater matrix? If you're trying to stop humid
air reaching the screen you should remove it by condensing it out
with the aircon heat exchanger whilst it's still cold. Once the water
content has been reduced it doesn't matter if you use the heater to
warm the dried air, as even if that air hits the cold screen it won't
have water in it to mist up the screen. If you try to do it the other
way round, it's much more difficult.
I had the same thoughts when I read that. It's how air handling systems
do it. It also allows for greater control of the final temperature and
humidity.
--
Davey.
John Rumm
2024-06-11 23:16:06 UTC
Reply
Permalink
Post by Jeff Layman
Post by John Rumm
Post by TimW
The modern world being what it is the latest old banger I am driving has
Air Conditioning - except that it hasn't worked since I have had it.
That wouldn't be a problem, I could wind down the window but the heating
doesn't work either and it was cold driving in the Winter. I wondered if
I needed to bleed air out of the pipes to the heater and turned what
looked like a bleed screw but then realised that gas was escaping and I
was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon fixed
might I expect the heating to work? Car is a Mitsubishi Colt.
It sounds like you probably have more than one issue...
It does - and more expense!
Post by John Rumm
Assuming that the heater part is "conventional" then there should be a
hot water feed and return to the heater matrix. This is what should heat
the air (either ram fed or fan fed) into the cabin. It is not unknown
for the heater matrix to be "bypassed" if it springs a leak (since they
are often well embedded in the dash and can be a PITA to replace). Also
check there is enough water in the radiator. On some cars there may be
additional valves / stats to inhibit flow through the matrix until the
engine is up to temp.
After the heater matrix, the air should pass through the aircon heat
exchanger.
No sorry - I wrote that backwards! It is usually setup to allow it to
warm up cold dry air
Post by Jeff Layman
Post by John Rumm
When the aircon is switched on you should hear / see some
activity as the compressor belt is engaged. (some systems also have a
sight glass where you can see if the cooling gas/ liquid is being
circulated). If working normally it will automatically cut in and out as
it maintains the required level of cooling. If the gas level is low, it
may run continuously and not actually cool much or at all. If the gas
level is *very* low it may not even fire up at all. The fix for both it
to get it re-gassed. They will normally assess if for leaks at the same
time, and add the right amount of lubricant to the gas as well.
If it's an old car I wonder what refrigerant will be used to regas it.
There will be an info sticker somewhere that will normally tell you the
gas used, and the mass of it required, often also what compressor oil to
add.

If it has the "wrong" type, they can often recharge them with a more
modern replacement. Some very old units may also need an adaptor to the
recharge point fitting.

My car is a 2008 model and the label has HFC134a gas - the refiller had
no problem with that - but possibly swapped it for HFO-1234yf. I think
on my previous car (2003) they had to recover the
--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
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\=================================================================/
Theo
2024-06-12 11:37:31 UTC
Reply
Permalink
Post by John Rumm
There will be an info sticker somewhere that will normally tell you the
gas used, and the mass of it required, often also what compressor oil to
add.
If it has the "wrong" type, they can often recharge them with a more
modern replacement. Some very old units may also need an adaptor to the
recharge point fitting.
My car is a 2008 model and the label has HFC134a gas - the refiller had
no problem with that - but possibly swapped it for HFO-1234yf. I think
on my previous car (2003) they had to recover the
If you have a very old car with an R12 system (early 90s or earlier), you
can convert it to take R134a.

If it's later but pre 2017 it'll take R134a.
If your car is post 2017 it'll take R1234yf.

It seems you can fill an R1234yf system with R134a, but not an R134a system
with R1234yf. You need to vacuum out the system so there isn't a mix of
gases.

In general a regas means vacuuming out the gas into a recovery cylinder then
putting in the manufacturer's recommended weight of fresh gas - they don't
reuse the old gas (it goes off to be reprocessed).

Cars with a belt-driven compressor usually take PAG oil, hybrids and EVs
with an electric compressor use POE oil. Getting even traces of PAG oil in
a POE system can burn out the compressor. This is why hybrids and EVs need
to be gassed on a machine that uses POE oil.

Most garages only have a single machine which has had PAG in it, so you
don't want to gas a hybrid/EV on them else you risk killing the compressor -
getting a new OEM compressor can be a £1k+ part, although scrappies often
have them for a lot less.

Theo
Andy Burns
2024-06-12 13:57:11 UTC
Reply
Permalink
Post by Theo
If you have a very old car with an R12 system (early 90s or earlier), you
can convert it to take R134a.
Wonder why car aircon isn't moving to R290 like fridges and ASHP?
Presume that doesn't need recovery, you could just flare it off?
Theo
2024-06-12 14:15:19 UTC
Reply
Permalink
Post by Andy Burns
Post by Theo
If you have a very old car with an R12 system (early 90s or earlier), you
can convert it to take R134a.
Wonder why car aircon isn't moving to R290 like fridges and ASHP?
Presume that doesn't need recovery, you could just flare it off?
https://aircontopup.com/shop/
is a mix of propane and butane, similar to fridges.
(R290 = propane, R600a = isobutane)

In a car there's worries about flammability and leaks into the cabin,
although you also have the fridge in your living space too. Possibly
there's a higher risk of an ignitable concentration in the smaller volume of
a car cabin than the average kitchen?

Theo

Theo
2024-06-11 19:48:13 UTC
Reply
Permalink
Post by John Rumm
Post by TimW
The modern world being what it is the latest old banger I am driving has
Air Conditioning - except that it hasn't worked since I have had it.
That wouldn't be a problem, I could wind down the window but the heating
doesn't work either and it was cold driving in the Winter. I wondered if
I needed to bleed air out of the pipes to the heater and turned what
looked like a bleed screw but then realised that gas was escaping and I
was further de-gassing the aircon.
Question: If the Aircon is bust or maybe just neeeds re-gassing will
that prevent the heating from functioning? eg if I get the aircon fixed
might I expect the heating to work? Car is a Mitsubishi Colt.
What vintage of Colt is it?
Post by John Rumm
It sounds like you probably have more than one issue...
Not necessarily - it could be a control system fault. eg lack of power to the
HVAC ECU means neither heating or A/C will turn on. Or 'something is wrong'
and the ECU has decided to shut down - eg broken temperature sensor and it
can't decide whether it's going to roast or freeze you, so it refuses to
do anything.

It would be worth doing an OBD scan to see if the car has any idea where the
fault might be, before diving in to poke wiring.

Theo
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