Air Conditioning Intermittent

My wife's 1997 Mondeo 1.8LX's aircon has started behaving strangely. It usually works fine, but on several occasions recently, it has stopped working while the car was sitting in a traffic jam. Once out of the traffic jam, it remains non-functional for a seemingly arbitrary time period (anywhere between 10 and 30 minutes), then starts working again. I am fairly certain that the compressor is still running when it's not working: turn it off & on, and the engine revs drop & increase as you'd expect.

So, we called out the local mobile aircon specialist, and he said the symptoms were not familiar to him. We did however decide to have the car de-gassed and re-gassed just to see if that fixed it. Unfortunately it didn't: exactly the same thing happened again a few days later.

My gut feeling is that it will cost a lot of money to get this fixed, and since the car is probably worth about zilch (10 year old Mondeo, 170k miles), it might be better to accept that the time has come to replace the old workhorse. But before we do that, I thought I'd ask here if anyone recognises the symptoms and can suggest a likely cause.

Thanks.

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Engine speed change is not conclusive that the pump is running, have a look and see it turn, feel the pipes, when it is working and when it isn't, note the differences. it could be many things, a pressure check when the problem occurs should show what the fault is. Possibles that spring to mind are dampness freezing at the evaporator and temporarily blocking the pipe (should be fixed by a good vacuuming) or a blocked filter/accumulator (about a forty quid bit) There are other possibles, but really it needs checking when the problem occurs, obviously you should check that the radiator at the front is clear and the fan is running. Mondeos do suffer with condenser problems, but usually they leak.

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I have the same problem with my Volvo

It has been suggested that the system trips out as the compressor can't reduce the temperature sufficiently due to the high outside air temperature

I wondered if it is to do with the cabin air sampling fan not working (mine doesn't at present) and the management system switching the air con off because it cannot get a reading? I feel that I an clutching at straws with this idea

I will be interested to see what the experts here say

Tony

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TMC wrote:

I've read that the compressor clutch can fail on Volvos, leading to this. What Volvo?

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V70 diesel 1998

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Tony - see my other post. I've sucessfully resolved this fault on my Volvo 850.

Alan.

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thanks for this I'll have a look when it stops raining

tony

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Many thanks to everyone for their comments. What it tells me is that I understand even less about aircon that I thought (and what I thought I knew was precious little). Cars are just too damn complicated these days.

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Are the cooling fans running with the air con on? Does the temp gauge sit any higher than normal when in traffic?

It could be that there's insufficient flow through the condensor, so when stationary, the air con is partially overheating so you don't get much cooling effect, but when you start moving, the airflow cools everything down, and the aircon appears to start working again.

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I've had exactly this on my Volvo 850, and would say there is a high chance your fault has the same cause....

It was caused by a worn compressor clutch, that engaged OK when cold, but when hot the expansion caused the gap to expand just enough for the electro-magnetic not to be able to overcome it. Once cooled down it then worked fine for a bit longer. Usually it needed the engine needed to be switched off for a while for it to cool enough.

I fixed it by removing the clutch plate, and changing the shimms (washers in this case) to close up the gap a little. I found the specified gap distance somewhere on the web and adjusted it to that. There were several washers of various thickness and by moving some to the other side of the plate I was able to get the correct gap.

Once re-fitted it then worked fine, and still is, 2 years later. In my case I had the system apart so removed the compressor and dis-assembled on the bench, which made it easier. I've performed the same operation on a Saab compressor in situ without removing the pipes as it was at the top of the engine.

Alan.

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