1996 A6 Quattro 2.8
My A/C will run fine for a while (though not too cold), then the compressor will just shut off. The car is not anywhere near the tempeture setting. It will come back on in about 10-20 seconds usually. Going to manual and pushing the compressor button does nothing. This continues until I give up and open the windows. It’s always happens when it’s really hot out, but when it’s cool out it seems to run just fine (when I don’t need it). Lowing the temp control to the bottom doesn't help either.
The former owner (friend of mine) had the system serviced last year for about $70, and the shop said there were no leaks. I knew the system was quirky when I bought the car. He replaced the Climate Control box with a refurb but the system ran the same. Hooked up a OBD2 reader and have zero codes. I will try to run the CC diagnostics tomorrow, but the range of numbers on both files available don’t seem to match up to my device. Will try it anyway and see what comes up. Any tips or suggestions?

boots

 

Sounds to me like you are low on refrigerant. Could be one of many things, maybe your orifice tube/expansion valve/condenser is partially plugged and tripping the high pressure switch. Maybe your low and tripping the low pressure switch. Do you have a set of r134 gauges?

Welcome to the forums. This is a great resource, get used the search function and enjoy the car.

Jeff

 

When your AC is working properly the compressor will cut on and off as needed. It is not supposed to run all the time. But in your case since it is not cooling like you say it should be, I would guess you might either have too little or too much freon in the system. I ran into a case on a 2.8l A6 once where a customer had their AC serviced at a Merchants tire or something and they over filled it with freon. Doing this can cause too much pressure to build up in the system and there is a pressure switch that cuts the compressor off to prevent it from damaging anything. Just possibilities. When the compressor is running, is the air blowing from the vents very cold?

 

The evaporator could be clogged as well. This will cause the compressor to cycle as it sees the temperature of the evaporator go down.

Bob

 

he can afford to use the AC[sm=jawdrop.gif]

 

I agree with Jeffla. Get some gauges and or have someone read your pressures. Start there. More than likely its low on gas. The evap/condenser would only be plugged if the system was previously opened and not properly evacuated.If the evap (liquid line) is plugged your discharge temp and pressure will sky rocket and trip the high pressure cut out.

Post your pressures if you would like more info.

Good Luck!
E

 

I was joking of course ( not a j/k in the UK though ) and yes refrigerant is probably low and the system automatically shuts down to prevent damage to the compressor

 

Don't have any guages, but will have it looked at today to see if it's too low or has too much.

I ran the CC diagnostics this morning and discovered a couple of things. First off, no air is coming out of the defrost vent, either by pushing the defrost button or using the manual flow control button. Also, code 29 (A/C Compressor speed in rpm) shows 000 with the car running and compressor on (it was cool this morning and the A/C was working, though not very cold).

Anyway, I'll run it by the shop in about 4 hours to see what they think.

Thanks for all the advice.

boots

 

Went to the same shop as my friend went before (my first choice was packed). Diagnosis...retards. They couldn't even figure out how to hook up the machine properly. I don't know how either, but I don't work in a garage. First, they connected the red line to the condenser, and then searched around the car for a second place to hookup a blue adapter. They couldn't find anything, so they just started the machine. It "recovered" 0.63kg of whatever, and then went into vacuum mode on a 15 minute countdown. After 3 minutes, it shut down. The guy started the vacuum mode again, and it again shut down at around the same point. He told me the machine was over-heated (which I thought rather ironic). He had me start the car and turn the A/C on. It was just a tad cooler than before, but not where I believed it needed to be. He looked at me to see if I would just say "O.K, thanks, here's $70, have a nice day!" Uh...no. So he chatted with the manager and he got on his cell phone and jabbered a lot with someone while looking at the machine. They were speaking in a foreign language so I couldn't understand (like the first time I heard a Scottish comedian). They ran it again, and it recovered 0.43 of whatever, and then failed again during the vacuum phase. He restarted the vacuum test again, [/i]and it what??? You guessed it…failed. I figured I would cut my losses and run. I think I ended up donating Freon to them, [/i]but no money.[/i] I will show up early to the first garage to make sure I get in this time. Morale of the story? Sometimes the heat makes you do stupid things.

 

I'll bet you have one of those AC systems that need the the special adaptor that connects to the low pressure side at the comprssor -like my 1997 Avant.

I work in N Billerica MA (live on the sacoast of NH) and am looking for a place that will check/refill the charge in my AC systemwithout it costing my first born or screwing up the car. If you find one let me know.