air con prob,+ parts wanted

[silversteve]

Hi all,im appealing to all air con guru's out there. Had the car in garage today to trace a fault on air con system,clutch kicks in for about 4 secs then cuts out,been re gassed,all pressure switches and relays checked all fine. When air con compressor was connected direct to battery it ran fine and pumped out nice cold air ........
BUT, mechanic reakons its the Fan Reheostat? bad spelling on invoice i think,if not, the control panel itself,as when removed it was covered in an oil type liquid all over the back and wires.
So i was hoping someone out there has a panel or fan resistor. Have included a piccy of bit needed,its for a 1993 2.8e coupe quattro,thanks in advance all,Steve

[rj scotty]

Inlet air temp sensor could be at fault, as could high or low pressure switch.

Try and bypass (temporary) the low pressure switch. It lives behind the glovebox and is a bitch to get to.

cheers

rich

[johne]

If your heater/A/C fan works when the knob is in all positions including max then all is fine, you've no problem with the fan speed resistor (rehostat as you've called it) or the panel control and anyway this isn't directly linked to the A/C.

The fact that you get cold air with the compressor directly engaged with 12 volts shows you have some gas but not necessarily the right amount of gas. My best guess is that you have too little gas or a leak that's brought you down to too little gas.

For the compressor to run normally F73 the low pressure switch has to be closed, i.e. enough gas in the system. The fact you run for 4 seconds suggests you have just enough gas to close F73 but that as soon as the compressor engages the pressure drops and F73 drops out.

You could have too much gas so as soon as the compressor engages the pressure in the switch on the rail in front of the radiator opens also causing the compressor to cut out but I think this is less likely.

Either way, you or your mechanic need to monitor what's happening to those switches. Finally, it could just be that J155, the A/C control relay has gone faulty.

Wiring details are on S2Central.net

John

[silversteve]

Thanks Scotty and John, the first thing i did was to by pass the pressure swiches, and your right the one behind the glove box is a real Beatch.......
The fan speed knob,dont seem to run on the lowest speed,notch 1, but then works on the rest of the settings. As for correct amount of gas,i guess you have to trust the air con guy,but the mech told me that the system has no leaks and the correct amount of gas was put in.......... The relays were checked and seem to work fine,but in the fuse box there are two relays missing,one for rad fan,and one for rad fan delay?? have attached piccy of fuse box the relay 214 top right is air con relay swapped it for the other 214 relay for fan speed 1 and still had same prob. As a matter of interest where is the best place to get hold of those relays,and also the ones that are missing,really dont want to go to the stealers............
Cheers all

[ChrisAudi80]

Hi all,im appealing to all air con guru's out there. Had the car in garage today to trace a fault on air con system,clutch kicks in for about 4 secs then cuts out,been re gassed,all pressure switches and relays checked all fine. When air con compressor was connected direct to battery it ran fine and pumped out nice cold air ........
BUT, mechanic reakons its the Fan Reheostat? bad spelling on invoice i think,if not, the control panel itself,as when removed it was covered in an oil type liquid all over the back and wires.
So i was hoping someone out there has a panel or fan resistor. Have included a piccy of bit needed,its for a 1993 2.8e coupe quattro,thanks in advance all,Steve

Resurrecting an old thread.

You say they connected the AC compressor direct to the battery and it works? It thought the AC compressor was powered by serpentine belt.

It seems as if turning on the AC in my S6 uses a lot of power. There is a significant drop in voltage in my S6 when turned on.
Some one has suggested that my high side pressure is too high thereby loading the engine too much.

If sitting in heavy traffic for a long time with the AC on, the voltage drops to 12v, sometimes below. The idle is also very weak and erratic. On tip in, the engine sometimes stalls.

EDIT: Fixed. My PRV valve installed wrong.