[Mk2] [Turbo] AC issue

[robbie_742003]

Hi all,
Just recently developed a problem whereby my AC is constantly running, regardless of whether the switch is on or off. The only way i can turn it off is by turning the fans off altogether or pull a fuse i suppose.
Has anyone else suffered with this that can help?
Im thinking a dodgy wire or relay?

thanks in advance

Rob

[Pauln]

This is probably one for the experts, which I'm not. But here's a few thoughts to be going on with.

So when you say it's constantly running whether it's turned on or off on the heater/ac controls can you hear the compressor cutting in and out or is that always running and the idle speed always raised.

One easy check would be to disconnect the single electrical connection to the magnetic clutch on the compressor. If the compressor then keeps running the clutch must be jammed. If the compressor drops out then it's obviously an electrical issue.

If the clutch is actually dropping in and out as the cabin reaches temperature and no further cooling is required, it might be worth checking the actual a/c switch on the heater controls in case that's faulty and is always "on".

Other than I guess it could be a faulty relay or a faulty a/c amplifier which I think is under the glove box. You also have a pressure switch in the frunk, but I wouldn't have thought it was that as I think that's just there to stop the compressor running if all the gas has escaped from the system.

But I think you really need to know what you are doing if you are going to try to check the system through, unless just try changing key parts to see if the problem goes away - but that's a bit hit and miss and there's no guarantee that it will be money well spent.

Paul

[shinny]

Just recently developed a problem whereby my AC is constantly running

As above.. can you explain exactly what you mean by this. (Or, how do you think you know that your a/c is constantly on?) Is it just that the LED is always on? Or is the air always cold no matter what you do to the heat slider? Or can you hear the aircon compressor turning itself on and off all the time? Or can you permanently hear the aircon compressor? (If so, how do you know it's that and not something else in the engine bay?)

Paul has already mentioned a few good points, but before recommending anything, I'd want to know exactly what the symptom is.

[robbie_742003]

Thanks for the replies chaps.
What I mean is that unless I turn the fan switch to 'off' the compressor will constantly be turning on and off (revs increase and I can hear it, and I know what it is ) as it would normally if the AC button had been pressed. Only now it doesn't matter if the button is on or off, AC compressor is running. It's only just started to play up and had been working fine up until last week. The slider works as it should, hot and cold as required. I've just pulled the fuse for the time being.
I'm not sure where the connection is for the magnetic clutch if you could help with its location?

Cheers

Rob

[Pauln]

From memory it's the only electrical connector coming off the compressor so is fairly easy to spot - and it's a single wire. The connector usually lives fairly near the 02 lambda sensor wiring and the connectors are interchangeable.

The magnetic clutch wasn't working on my tubby when I bought it, and as I'd just had it regassed, the pressure switch was giving out a control voltage and the engine tickover was raised when aircon was turned on, we rashly assumed it was a faulty compressor.

Unfortunately when we came to fit a replacement compressor we found that a previous owner had cross plugged it with the lambda sensor

So we may not have needed to change it after all. I don't get quite the same kick up the backside when I put my foot down now, but fuel consumption seems to have improved

Paul

[robbie_742003]

Cheers for the help Paul, will have a look at it this week.