air conditioning diagnostics
 

I would appreciate some advice please. I have just replaced the CCM and I now have a working climate control. Unfortunately, the air conditioning is not engaging. The A/C light turns on/off and there are no stored DTC codes.

I have read the A/C pressure sensor via VIDA and get only 30 kpa. The specs state 170-320 kPa so it appears there is little/no gas in the system. I tried engaging the A/C relay via the diagnostics but there was no audible "click" and the clutch did not engage. Is that correct behavior when gas pressure is low (ie to avoid damaging compressor) or do I have a faulty A/C clutch and/or relay?

Anything else I can check before I take a trip to an A/C specialist?

Thanks!

Keith

Just go to one of the fast fit shops , most only charge if they get it working £50 or less if service is on offer.

afaik you are correct. Low pressure will inhibit a/c start to protect the compressor.

Was the engine off or running when you carried out the above checks?

It was running.

Keith

Low pressure will prevent the compressor engaging. On many cars, you can bypass the sensor but the risk is that you damage the compressor in doing so.

I think I have done all I can on it. David Pengalley in Nottingham is close by so will give him a visit. They were very well regarded when we had our 940!

Keith

You could actually have good gas pressure but a dead ac pressure sensor in which case, bridging the plug contacts could get the compressor working but it is also risky if you genuinely have no gas.

Working pressure sensor resistance figures should be in Vida should you want to get a multimeter on it.

OK. I understand. I think I will call it a personal day on the A/C though. That car has sucked a lot of time getting all the various faults out and I still have servicing jobs to do. The wife will just have to spend some money :-)

Cheers,

Keith

As suggested earlier, a £50 regas at a high street centre could be a cost effective route to diagnosis.

If you have a leak, they can't regas so won't charge.
You then know that your pressure sensor is most likely working and doesn't need replacing so your money can go towards fixing the leak.

If you don't have a leak and it holds good pressure using the garage pressure gauge but your pressure reading is still duff, your pressure sensor is faulty and there are plenty available for reasonable money.