Air Conditioning Compressor Trips out at Idle

[rj8994]

Hi,

I have an issue with my A3 2.0 TDI 2004. If I am at idle for more than 30 seconds (sitting at lights for example) the engine vibrates a bit then the compressor trips out (the econ button illuminates) and the only way to get the compressor back on is to turn the car off. Driving about its fine and will go forever, but when I stop especially if its hot it will trip out.

I recently have had the clutch on the alternator replaced (it was doing this before and I thought that would have sorted it). The compressor was replaced under warranty (3 years ago) but from memory when that went the air con was never on. I have never recharged it and its 6 years old.

I read the informative Air Con FAQs but it didn't give me any answers on this problem, is it common?

Many Thanks

Karl

 

[Staz]

Not heard of it personally. It could be a pressure thing. My first guess would be that your condenser is a bit blocked or maybe the fan has died (although the symptoms of that should be more obvious). If not enough air flows through the condenser to condense the refrigerant (because you've stopped moving) the HPCO will trip and shut the system down.

Try starting the engine while stationary, turn the air con to lo and check the fans run, then have a look for blockages in the condenser matrix. The condenser is attached to the radiator BTW.

 

[rj8994]

Thanks, sorry I was waiting for the forum to email me when someone posted, but it didn't.

Might be that actually because when you go along you can feel the air coming out faster. I just tried it (though its typical cold weather today so doesn't have to work that hard) and the 2 fans at the front of the car didn't move. I will wait until warmer then try again. Do you know if its the left hand one or the right when when you are looking at the car that should move?

Karl

 

[Staz]

I can't remember which fan is it but if the air con is on and it's set to low one of them SHOULD be running.

 

[rj8994]

Hi,

Ok there are 2 big ish ones at the front and when the compressor trips out none are running. I assume one will be the 'normal car fan when it heats up' which I guess the car wasn't hot enough because I only just switched it on and the other should be for the air conditioner and should have come on?

Kind Regards

Karl

 

[Staz]

With air con on one should be turning for sure. If the engine needs cooling (with the air con off) I don't know if just the other fan turns or if both do i.e. the air con fan doubles as an engine cooling fan.

Either way...with the air con set to low, the engine cool and BEFORE the compressor trips does one fan turn?

 

[rj8994]

No it trips out and no fans are turning

 

[adamss24]

Then its either the fuse blown or the fan is not working thus the ECU turns the AC off...do a dignostic scan and see what is happening...

 

[Staz]

Right I don't think you're fully answering my question. You say the compressor trips after about 30 seconds of being stationary, does the fan run whatsoever before that?

I would have thought the whole air con would be disabled well before 30 seconds if the fuse is blown but it's always worth checking.

 

[rj8994]

HI,

When I did the test I just started the car (from cold) and waited for it to trip out, neither of the 2 fans started. I got someone to look at the fuses but none were blown. Could it be something up with the FAN?

Karl

 

[Staz]

Yep sounds very likely mate. VCDS might be able to confirm it but no guarantees.

 

[PW-Motorsport]

Check what pressure you have in the aircon system when it it running at idle 4/6 bar should be about correct on a 10/15deg day.

If the pressure climbs on start and the fans have not cut in, check the power to the fans.

 

[rj8994]

Hi,

You were right it was the fans, both of them. They are not a cheap piece of kit either. I don't understand it fully, but one controlles the other and it went wrong and can cause the other to burn out. So basically both fans at the front were burnt out causing the compressor to over heat and trip out. This was solved by replacing both fans at a cost of 205+VAT for fan 1 and 126+VAT for fan 2. Labour was not expensive 90 + vat, total bill over 500.00. A lot but the parts are expensive! I went to a really good garage in Oldham (volksmaster who diagnosed it and fixed it).