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[biggriffin]

Switched off eco, set to low, fans on full, fuse ok. Still not switching in the compressor  . Any ideas?

I would say no refrigerant.

[Kevin Wood]

Either high pressure or low pressure will prevent the air conditioning compressor from engaging. I can't remember where the pressure switch is located but it rarely gives problems, and replacement would require the system to be vacuumed out and refilled anyway.

Do the front fans run at slow speed when the air con is switched on? If they do, but the compressor doesn't engage, I'd suspect a problem with the compressor clutch (you can get to the wiring to this from underneath the engine). Otherwise, assuming the fuses are OK, the most likely issue is low refrigerant but it might be worth checking if relay K60 is engaging. This is in the triangular box by the passenger side front wing. On the row of relays closest to the wing, it's the 5th relay back from the front.

If you remove this relay, take its' cover off, then re-insert it, you can watch for movement when you turn the air con on. You can also push the contacts together with the ignition on and you should see the compressor clutch engage and the fans start.

[biggriffin]

High pressure switch is located, on the pipe, just above the under tray, in front of compressor, has a two wire plug on, only replaced one, £65.00.

Earlier models had a high and low pressure switch.

[mandula]

My A/C has also stopped working.

After winter when hot day I noticed lack of cold air coming from nozzles and compressor did not engaged.
I took it to A/C service where they refilled the system and after that A/C worked fine (cold air coming and compressor engaged), until the next day it did not work again. No cold air and compressor does not engage.

I viewed live parameters with OBD-tester via phone application and it said there is A/C-pressure of 1000 kPa (~10 bar).
I could also test A/C-relay (I don't know which relay) from this application and it made fan to start up at engine bay .
I've measured that compressor magnetic clutch resistance is OK 4.3 ohm.
Fuses are OK.

I assume there is no leak because of A/C-pressure reading says there is pressure (does that pressure reading sound about right?).
Is there a way to force engage compressors clutch from relay box, to check there is no open circuit on wirings?
What else could I check before I go back to A/C-service for troubleshooting and giving away my money?

I don't know are these related, but just after A/C-service car's Check control informed me about "Check oil level". There was oil enough and that message keeps coming and going randomly many times a day.

[LC0112G]

My A/C has also stopped working.

After winter when hot day I noticed lack of cold air coming from nozzles and compressor did not engaged.
I took it to A/C service where they refilled the system and after that A/C worked fine (cold air coming and compressor engaged), until the next day it did not work again. No cold air and compressor does not engage.

I viewed live parameters with OBD-tester via phone application and it said there is A/C-pressure of 1000 kPa (~10 bar).
I could also test A/C-relay (I don't know which relay) from this application and it made fan to start up at engine bay .
I've measured that compressor magnetic clutch resistance is OK 4.3 ohm.
Fuses are OK.

I assume there is no leak because of A/C-pressure reading says there is pressure (does that pressure reading sound about right?).
Is there a way to force engage compressors clutch from relay box, to check there is no open circuit on wirings?
What else could I check before I go back to A/C-service for troubleshooting and giving away my money?

I don't know are these related, but just after A/C-service car's Check control informed me about "Check oil level". There was oil enough and that message keeps coming and going randomly many times a day.

That's far too high if the compressor isn't actually running. From memory (admittedly on the Carlton) it's about 3-4 bar when not running, up to 8-10 bar running on the HP side. Omega may be a bit different, but 10 bar static can't be correct, so assuming your Reader is working properly I'd suspect either the sensor or wiring to the sensor.

Or perhaps more likely, it's reading 1Bar (i.e. Atmospheric), there is no gas in the system again, and you've got a big hole in the AC radiator. 

[Kevin Wood]

The Omega has no pressure sensor anywhere in the A/C system so there is no way for this data to be presented by OBD. I think it's a red herring.

[mandula]

It really is 1000 kPa, it sure might be 100 kPa so it might be normal surrounding pressure.

I read somewhere that there is some analog pressure sensor that gives pressure reading in voltages to ECU or what ever is controlling A/C system?


Well, I made some testings and took hats off from relays K60 and K87 under bonnet. Car was running.

When I pressed contacts on relay K87, both fans switched ON.
When I pressed contacts on relay K60, both fans switched ON and compressor engaged.

So I believe all wirings are OK.

I believe now I have about three options left and one extra option:

1. Pressure too high (I don't really believe so because A/C worked fine for one day).
2. Pressure too low.
3. Pressure sensor/switch defected.
(4. take it to the service  )

Maybe next I'll connect OBD-reader again and check if pressing pressure valve gives me any PUFF and if so, does that affect the reading I see on live parameters..

[mandula]

Ok, almost none PUFF when pressed valve. To the service it is then 

Next time I test that method first and dont trust any stupid false nonsense readings that applications give..

[biggriffin]

It really is 1000 kPa, it sure might be 100 kPa so it might be normal surrounding pressure.

I read somewhere that there is some analog pressure sensor that gives pressure reading in voltages to ECU or what ever is controlling A/C system?


Well, I made some testings and took hats off from relays K60 and K87 under bonnet. Car was running.

When I pressed contacts on relay K87, both fans switched ON.
When I pressed contacts on relay K60, both fans switched ON and compressor engaged.

So I believe all wirings are OK.

I believe now I have about three options left and one extra option:

1. Pressure too high (I don't really believe so because A/C worked fine for one day).
2. Pressure too low.
3. Pressure sensor/switch defected.
(4. take it to the service  )

Maybe next I'll connect OBD-reader again and check if pressing pressure valve gives me any PUFF and if so, does that affect the reading I see on live parameters..

Basically you've over analysis's a simple problem, you need to see if the system will hold refrigerant, if it will, then look into why it's not working, my money is on either leaking condenser or leaking compressor, or holes in pipes under battery tray.

[mandula]

Yea, as stated above your post I noticed there was almost none stuff in the system.

I was confident that I could trust the live parameter reading of A/C pressure. I was wrong. But now atleast I know better how my A/C system works 

[Omega Nige]

Hi all sorted, see my thread in the electrical section, thanks for your input

[Omega Nige]

Hi, thanks for your help all sorted see my post in the electrical section