Air Conditioning Problem

Krister said:
RAB, it's a variable displacement compressor on the 1.4 Petrol, so no clutch. Compressor turns as it should and it does increase pressure in the system, just not as much as one would expect.
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All A2 have variable displacement compressors. If the compressor seizes, the pulley will release itself from the compressor to save the belt from breaking. It's not a clutch, that's why I used "clutch", just a rubber coupling.

RAB
 
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Ah, sorry RAB, didn't read your post carefully enough. I thought perhaps the 1.2 had a magnetic version to save on fuel... :)
As far as I can tell the compressor rotates as it should (visual check + increased pressure) but it's worth a more thorough check.
I'll dig into the panel this weekend as well and see if something's wrong with the temp flap.

Don't know if the end point readings for the temp flap make any sense to you: Measuring block 003: I've got 27.0 and 232.0 as the set points and it does appear that the potentiometer reads these values as I go from LO to HI setting on the climate control.

Thanks,
Krister
 
A basic check - Not sure if it's been covered but the main radiator fan should run on low speed as soon as the air con is switched on - even when the engine is cold.

Cheers Spike
 
My compressor stripped the safety inner plastic part, I had to replace it with a second hand one. The symptoms for future reference were no fault s on vcds, no cold air. It can be easily seen as if they aren't stripped the centre of the compressor pulley is attached to the pulley outer groove.

With the engine running the centre of the pulley stays still it needs replacing. It should all
 
Thanks for the tips. My compressor rotates the whole package so appears to be good - on the outside at least.
Radiator fan comes on as per specification, I can see it switch on in VCDS as well when I go from "ECON" to "AUTO" for example.

Is it safe to assume that if the high pressure pipe going into the cabin is cold, there should be some cooling effect out of the evaporator even if it isn't exactly arctic? Or, is the mass of the evaporator great enough that it requires a really frosty temp going in in order to create some cooling effect at all?
 
Krister said:
Is it safe to assume that if the high pressure pipe going into the cabin is cold, there should be some cooling effect out of the evaporator even if it isn't exactly arctic? Or, is the mass of the evaporator great enough that it requires a really frosty temp going in in order to create some cooling effect at all?
Click to expand...

The high pressure pipe will (or should, unless you are low on refrigerant) contain liquid; the cooling effect only occurs when the liquid becomes a gas (in the evaporator). If you place a thermocouple on the pipe, you will probably find that it is at near ambient temperature.

RAB
 
I was under the impression that the liquid becomes a gas after the expansion valve (restrictor) which is before the evaporator in the high pressure line. That's where I feel the temperature drop, it's just before it enters the bulkhead.
It is not at ambient temp when the AC is switched on. The high pressure pipe is slightly colder than ambient also before the expansion valve probably due to cooling though the condensor. I know this because I felt the transition from ambient to cool as the AC system was switched on.
The Low pressure side is warmer than ambient as it exits the bulkhead.
Does this seem abnormal?

Edit: Actually, it becomes a gas in the evaporator as you say (hence the name...). Nevertheless, the liquid cools down after the restrictor but I'm pretty sure it doesn't get to icy cold at that point as it probably should. I guess it could just be a matter of the compressor not working properly - i.e. as in low compression due to blow by or something? Worn piston rings?

Krister
 
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Best way to judge is to monitor the change in pressure after the A/C is switched on. The HP is the smaller of the two lines. The compressor doesn't have any piston rings. Does the shaft of the compressor (the inner part of the pulley) turn with the pulley? If not, the compressor is not working.

RAB
 
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