lube
Registered User
Hi All,
First post here, got quite a strange air-con problem that I'd appreciate any help diagnosing. Car is a 2003 A4 B6 1.9tdi (engine code AVF). Have just replaced the G65 pressure sensor to no avail. Here are the symptoms:
Based on the above I think this means:
A few things I was wondering:
As you can see I have done a fair bit of diagnosis and probably replaced the G65 sensor for no reason, so any help would be appreciated!!!
First post here, got quite a strange air-con problem that I'd appreciate any help diagnosing. Car is a 2003 A4 B6 1.9tdi (engine code AVF). Have just replaced the G65 pressure sensor to no avail. Here are the symptoms:
- Air con worked last year, but this year was blowing warm.
- Last year the ECON light stuck on for a while under a wee
- Had not been re-gassed since I owned the vehicle (5 years) so had system professionally re-gassed using an automatic machine that flushed, tested, lubricated and re-filled.
- Immediately after the re-gas the air con was still blowing warm air, both when vehicle stationary and under motorway driving.
- Fuses on box by drivers side door all intact.
- ECON light off (but goes on if I disconnect the G65 pressure sensor or corresponding 5A fuse).
- VCDS lite not reporting any relevant fault codes (codes re engine mount and steering angle sensor assumed irrelevant). The first time I checked this a few days ago I got no faults. I thin re-checked and got an "00819 high pressure sensor (G65) 29-10 short to ground - intermittent", so I replaced the sensor with a brand new hella-behr part. Thinking about it I was pulling the fuses to check if the econ light went on/off, this may have been the cause of the fault code.
- Auxiliary fan not coming on, voltages at the 4-pin fan connector next to the PS reservoir don't change when I switch ECON on/off.
- No drop of engine revs when I switch ECON mode on/off.
- Air con compressor pulley seems fine, can't see or hear any problems.
- VCDS reports a Refrigerant Circuit Pressure of 5.0 bar and a High Pressure Signal (G65) of 20.5% at about 18C ambient temp, which according to VCDS is about right.
- G65 pressure sensor replaced, fault codes cleared, air con still not working, no aux fan etc.
- VCDS compressor shut-off criteria: all 0.0
- VCDS Compressor torque status: 0, Required Engine Torque: 2.0 Nm
- A/C valve (N280) current: 0.648 A
- A/C valve (N280) duty cycle: 62.4%
Based on the above I think this means:
- The aux fan is not the problem. If it was, the air con would still blow cold under motorway driving (as in this thread)
- The G65 sensor may have been faulty, but now it certainly isn't.
- The compressor is not starting.
- According to the shut-off criteria being all zeros, the compressor should be running.
A few things I was wondering:
- If the compressor was faulty, would the aux fan run anyway? According to this thread I suspect the fan only starts if the pressure is above a certain point, i.e. if the compressor is running.
- How to work out if the compressor is faulty?
- What other diagnosis checks can I do?!!
As you can see I have done a fair bit of diagnosis and probably replaced the G65 sensor for no reason, so any help would be appreciated!!!