Hello guys,

I'm having a bit of a problem with the air con in my 56 focus st it's the dual climate control system.

A few months back I got the system regassed due to it not been cool enough.

After the regass all was great until a few days later sat at some traffic lights the air con stopped blowing cold.

After a couple of hours or so it worked again but only for 10 minutes or so.

So took it back to the chap who regassed it who did the relevant checks to find no problem at all, all pressures fine so no leakes, all sensors fine so no electrical problem.

The compresser does as it should when the air con works but when it stops so does the compresser of course.

He then plugged his computer into the car to see what's going on and nothing comes up as a fault and it detects the air con is on via the climate control unit but nothing, no fault codes nothing, the air con specialist is scratching his head at this, please any ideas anybody???

Could it be a fault with the cabin temperature sensor?

Where would I find this? Will it be part of the climate control unit?

Yes, it is part of the climate control. I don't know the interior of the later models, mine's a Mk1.5 as you can see from my profile. My model has a small grille on the console where air is drawn from the cabin over the sensor. This seems to be a common arrangement so I would imagine yours would be similar. I expect someone with more detailed knowledge of you model will be along soon.

I just had a further thought, though. As you probably know when you press the demist button this switches on the aircon. Next time it goes off you could try pushing this button to see if that turns it back on. If it does that would rule out a fault with the aircon itself, I'd have thought.

No it didn't work when I switched the demist button, opened the bonnet to find the compresser is doing nothing, but what's strange the car was sat on the drive for about 15 minutes with the air con on full, the car inside was like a fridge but soon as I set off driving it stopped

I know you said the guy did a pressure test but that wouldn't necessarily show up a leak. Normally they have to put dye in the system and you run it as normal for a week or so. They then get the ultra violet light out and search for the leak in the system.

When the problem started it was 3 weeks before I got back to the chap who done the job, he said himself no leaks so that's not the problem

The rad at the front can leak at the bracket on the front where its riveted on i was told no leaks 6 times till they put dye through the system the temp sensor on vws was behind the little vent where youre rear demister button is

This is from a Mk2.5 but I suspect the Mk2 is probably the same. If your Electronic Dual Automatic Temperature Control panel looks rather like this :-

then there are two sensors that the EDATC uses .

The internal cabin temperature sensor is located behind the little horizontal slatted grille between the switches (see pic above). Note that the sensor itself is not directly behind the grille but is set back about 5cm or so with a funnel shaped tube that links the grille to the sensor. The temperature sensor uses four wires; Brown/Green, White/Green, Green/Black and Black.

There is also another 'sunload' sensor under a small dome (about 15mm diameter) that sticks up from the centre of the dash panel about 8cm back from the bottom of the windscreen; it senses the light coming in via the windscreen. The sunload sensor has three wires; Brown/Blue, Grey/Violet and White/Blue.

I would have expected the demist button to override the cabin temperature sensors so if pushing it doesn't bring the aircon back on I'd suspect one of the aircon components.

As the problem only appeared after a re-gas (I assume it was working reliably before even though not cooling effectively) this does point to the aircon system itself.

I can't say for sure if it had this problem before the regas due to only owning the car about 6 months

When you say regas do you mean regas - refrigerant recovered, drier replaced, vacuum down, refrigerant and bit of oil back in or do you mean a bit more gas was added to what ever was already in the system? If the later what was the criteria for the ammount of R134a put in?

You also said it works fine when sitting on drive idling, but stops as soon as you pull off? Is this repeatable, and if so, I believe tha carputer uses lots of the sensors to see if it can give power to the aircon. Are there any other strange things going on with day to day driving?

Theres not enough pressure in the system suggesting a leak or one of the high ir low pressure switches is faulty a mobile specialist should easily diagnose the issue

Hi guys, yes the system has had a service twice, the first time it was done is when I went back to the same guy who did a full diagnostics with his computer to locate the fault.

No faults where found and the guy who is a specialist has no idea what's wrong.

Then 2 weeks ago took it to another specialist who checked everything over to find the system is holding its gas with no leaks.

He found the low pressure was a little high at 2.5 bar so he set the machine off to do a service.

After this service he got the low pressure just under 2 bar which he said it had to be.

The car was sat for about 20 minutes and the aircon was working fine until I drove away then it stopped working like it has done since the first service, so that's 2 specialists who have no idea what's wrong

Sounds like the pressure switch is faulty is the rad fan running with aircon on

Yes the main radiator fan runs, even when the air con stops the fan still runs