aircon

trevorswaine

trevorswaine

Member
New-Zealand
A small problem. The aircon works fine just driving along (regassed not too long ago) but on tickover it's much less effective. Got stuck on the M25 a couple of weeks ago when the temperature outside was 30 degrees and it got to be more than that inside the car.
Any suggestions much appreciated.
 
Check that the radiator fan is running at all times when the Aircon is switched on. The aircon needs airflow over the condenser. At speed there's always airflow, at idle no airflow unless the fan is running and hence very poor cooling
 
As above you would think that the fan isnt working. If it is then the gas pressure may be super low and about to require a re gas. You should see 4-6 deg c at the centre vent on low.....
 
trevorswaine said:
A small problem. The aircon works fine just driving along (regassed not too long ago) but on tickover it's much less effective. Got stuck on the M25 a couple of weeks ago when the temperature outside was 30 degrees and it got to be more than that inside the car.
Any suggestions much appreciated.
Click to expand...
If the load of the AC compressor is too high for an engine on idle, the ECU will reduce the compressor flow rate to minimum, to ease the load on the engine. Sounds like what you're seeing, I reckon.
Mac.
 
is the G65 working? If that is dud, even if the circuit is at the correct pressure you won't get cold air. However, what you mentioned about airflow speed having an effect on the ability of the system to generate cold air suggests that something is amiss with the fan interface with the a/c heat exchanger. I know that my A2 now audibly has the fan running at high most of the time when the a/c is on on the hotter days - much more so than more normal Scottish daytime air temperatures so the fan controller is clearly being instructed to turn the airflow up in response to demand.
 
trevorswaine said:
A small problem. The aircon works fine just driving along (regassed not too long ago) but on tickover it's much less effective. Got stuck on the M25 a couple of weeks ago when the temperature outside was 30 degrees and it got to be more than that inside the car.
Any suggestions much appreciated.
Click to expand...
In high temperature conditions the design parameters will be exceeded, the human body only needs to see about a 4-6 c difference to feel cool
Try setting a higher temp & see how the car feels.

Hope that helps
Keith.
 
PlasticMac said:
If the load of the AC compressor is too high for an engine on idle, the ECU will reduce the compressor flow rate to minimum, to ease the load on the engine. Sounds like what you're seeing, I reckon.
Mac.
Click to expand...
Static in traffic, at 30C ambient, the engine load, mainly from the alternator and AC will be high. Cooling demand is high, engine speed is low.
The cooling fan takes a lot of current, which the alternator tries to balance. Current demand high, engine speed low.
At idle, the engine power is low, unless the load is reduced, the engine will stall. The only load that can be shed is the AC, so that's what the ECU does.
I think what you're seeing is normal operation. Once engine speed increases, the load is the same, but the engine power is much higher, so the ancillary load is not a problem.
Mac.
 
I drove round Longleat very slowly last year (it took more than an hour half) on a very hot 34deg i think, day, the car stayed lovely and cool all the time, so it should be able to cope
 
steveb said:
I drove round Longleat very slowly last year (it took more than an hour half) on a very hot 34deg i think, day, the car stayed lovely and cool all the time, so it should be able to cope
Click to expand...
To me that's the fans purpose, it's very effective flat out. Maybe the op's system is tired, lowish pressure and tired compressor and or blocked dirty condensor.....
 
PlasticMac said:
Static in traffic, at 30C ambient, the engine load, mainly from the alternator and AC will be high. Cooling demand is high, engine speed is low.
The cooling fan takes a lot of current, which the alternator tries to balance. Current demand high, engine speed low.
At idle, the engine power is low, unless the load is reduced, the engine will stall. The only load that can be shed is the AC, so that's what the ECU does.
I think what you're seeing is normal operation. Once engine speed increases, the load is the same, but the engine power is much higher, so the ancillary load is not a problem.
Mac.
Click to expand...

WHEN ours was working, it would work fine, stuck in traffic or otherwise. The same goes for other cars and makes that I've had experience with. Maybe some variation with the RPM to get the pump running but not by that much.

I would start with:

1. a simple ac gauge diagnostic test (high/low side readings when ac on/off)
2. then a leak inspection
3. VCDS diagnosis.
4. multimeter tests on the respective sensors/actuators to make sure the VCDS agrees.

Potential culprits would be the metering valve on the comrpessor itself and the vent temp gauge sensor. Apologies but I cannot remember their names. The one behind the dash is pretty difficult to get to but it is easy to figure out whether it is lying or not via VCDS.

Evros
 
Evripidis said:
WHEN ours was working, it would work fine, stuck in traffic or otherwise. The same goes for other cars and makes that I've had experience with. Maybe some variation with the RPM to get the pump running but not by that much.

I would start with:

1. a simple ac gauge diagnostic test (high/low side readings when ac on/off)
2. then a leak inspection
3. VCDS diagnosis.
4. multimeter tests on the respective sensors/actuators to make sure the VCDS agrees.

Potential culprits would be the metering valve on the compressor itself and the vent temp gauge sensor. Apologies but I cannot remember their names. The one behind the dash is pretty difficult to get to but it is easy to figure out whether it is lying or not via VCDS.

Evros
Click to expand...
The OP says:
"The aircon works fine just driving along (regassed not too long ago) but on tickover it's much less effective"
I think a leak, or faulty sensors are unlikely, since they are not engine speed related. A tired compressor is possible though. Get a local AC man to check pressures, and go from there.
Mac.
 
I would get a vent temp gauge (looks like the one used for roasting) and check stationary vs moving.

It has improved the quality of my readings significantly. Can also be used to check the temp on your aquarium!
 
Thanks everyone for all your suggestions. I'll see if I can get it sorted at some point. It's a new problem, never noticed it in previous years.
I'll check the radiator fan first. Don't think there's a leak, the garage that regassed it would have reported it (I did ask them about it).
 
they wouldn't (shouldn't) have filled it if failed the leak test. it's now breaking the law if they do
 
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