A/C compressor clutch

[alg]

A/C working fine. New condensor dryer and the 'usual leaking' hose sorted. Today did not work. No telltale rpm blip on switching on. Then later the same day works fine.
Am I right in thinking this excludes the relay and compressor making the clutch the problem ? Or am I missing something ?

[4WheelDrifter]

Check the wire that goes to the compressor clutch. There should be just one (green?) cable that should get 12V when you switch the A/C on. IIRC if low or high pressure is detected the clutch is not told to engage.
HTH

[alg]

You mean pressure from the clutch rising as it fails ??

[4WheelDrifter]

Sorry. I meant pressure in the A/C system. The clutch is either on or off.

[alg]

What apart from gas loss would cause that? When it worked today it was as cold as always. Is there any atmospheric influence possible ? (Cannot think how as sealed system)
And if gas low to point of stopping clutch how could it re pressurise, if you see what I mean.

After it had 'that hose' done it passed the audi pressure tests (but then it did befoer as the flexible hose joint leaks slowly)

It has been serviced with oil twice in the last 6 months. guess compressor seal could be failing ?????????????????????????

[4WheelDrifter]

I was just thinking it could be a faulty high or low pressure switch causing it. That's where the digital climate with diagnostics is much better, but that isn't helping you, sorry. If the ambient temperature is less than 5 degrees, that will also prevent the clutch engaging.

[alg]

Its July in Scotland but even here its above 5oC !!!! But the switch makes sense with the intermittent nature of the fault. Where are they?

[Lloyd]

Hi Alg,


What is "that hose" for the un-educated by the way?

Hope you get to the solution OK.

Cheers,

[4WheelDrifter]

Its July in Scotland but even here its above 5oC !!!!

I know it's >5°C, but as long as the A/C system know it is. If the ambient temperature sensor is at fault it won't. Is your ATD reading ok?

IIRC the pressure switches are on the top rail on the condensor.

[4WheelDrifter]

I've looked at the A/C diagram I have and the low pressure switch is somewhere between the evaporator and the accumulator. So that'll be on the pipe that goes from the heater box on the bulkhead, to the accumulator in the wing. If the RS2 system is similar to the 3B.

[alg]

ATD has never worked due to cuircuit board fault. All bits to it work ! Condensor new so that should eliminate pressure switches.

[alg]

Hi Alg,


What is "that hose" for the un-educated by the way?

Hope you get to the solution OK.

Cheers,

See this excellent AC thread started by Angus. Hose makes appearance half way down

http://www.s2forum.com/forum/showthread.php?t=15700

[alg]

Weird. Worked as normal from start up. At midday collected car from carpark....no AC not kicking in....got home, checked plugs to condensor seemed secure. AC started again with lots of cool air hummm

[Animal Mother]

From past experience with AC, non Audi but Land Rover so I am a bit of an expert
Put a tester on the AC switch, the internal thermostat/thermistor, the + feed for the clutch and the earth/- for the clutch. Sounds like a dicky contact/faulty thermostat/thermistor/faulty AC switch to me.

[alg]

May have solved this one. Remind me, are pink deposits a sign of a leak with a system with leak dye in it ? The pipe running from the condensor back down to the bottom of the engine bay and on to the connector on the bulkhead has obvious pink deposits around one of the rubber pipe/metal connectors. Sorry no UV light or picture (it would not show up)
If I had a slow leak it may cause intermittent operation due to pressure drops in the system Any thoughts??