Air conditioning failure

[JHM 233]

Well it looks like the good weather is upon us again and sadly my air-con ain't working, it was serviced last august and re-charged by an independent, but i thought it was a bit pricey at £140 for a couple of hours work, have been switching it on every so often during the winter months as i was told to do, but it ain't working anymore, when i switch it on the compressor at the front of the engine turns for about 4 seconds then stops for the same time and keeps doing this, has anyone out there suffered from this problem or might know what will cure this problem, i thought it might be a faulty relay but i don't even know if there is one on the air-con system, the car is a 1996 850 2.5 10v CD, any advice would be great. Thanks, John

[SG]

It sounds like you're low on refrigerant which, given the system was recharged last year, probably means you've got a leak.

The AC system is the achilles heel of the 850. I hope for your sake that it's something simple like a loose connection but there's a good chance that the evaporator is the problem. It's a pretty big job to change it because the entire dash has to come out.

You can get the system recharged with coloured dye to see if and where it's leaking.

[JHM 233]

Thankyou for the reply, im hoping it's just needing a recharge because i don't think i could justify the cost of a new evaporator. Will book it in tomorrow as im sure i was told it was guaranteed for a year and that i would get a free recharge if there was a problem, but as usual i can't find the receipt, so much for my relay theory ha ha. the car was fitted with the dye you were on about as there was a sticker under the bonnet saying this when i got the car back in august, but i can't see any traces of the dye anywhere. thanks again john.

[vjck_uk]

In theory the system should never need recharging, unless it's got a leak.
You don't have your fridge and freezer recharged every year do you?

[Ben O Brien]

Its more than likely leaked its refrigerant,R134A im guessing,i dont know much about air con but one of my dads business' do air con so picked up a bit over the years,
I couldnt tell you where the leak is most likely to be though,im not that familiar with 850 air con,
The reason it was 140 quid was the price of the gas,its really expensive,
I have put a custom aircon system in my 242 and if the 850 system is similar my guess is the condensor is cracked,but as someone already suggested it may well be the dreaded evaporator...

the reason that most car air con systems lose refrigerant to some degree over time is due to the fact that have to operate in a enviroment that is somewhat harsher than your average fridge, the ideal conditions for a refrigeration unit are vibration free, and in constant use ,therefore two main problems arise in a car system,one, most car systems are used infrequently(in the uk at least) which causes seal degregation due to seals "drying out", and two, couple this with the constant flexing/stress inflicted on joints etc caused by extreme heat fluctuations, vibration etc, all lead to some losses being inevitable, however this amount should not be more than about 15 percent per year, anything more would suggest a "real" leak, the best preventive medicine for a air con system is use it as often as you can

[liuleichan]

>In theory the system should never need recharging, unless
>it's got a leak.

Yup, good theory.

>You don't have your fridge and freezer recharged every year
>do you?

Nope - but then fridges / freezers tend to use slightly different materials for certain components; don't have to work with the heat, virbation, and other environmental and external issues of a car engine bay, and perhaps lastly of most importance - tend to be used almost continuously.

[gary1638]

You won't see any leak with the dye unless you use an ultra violet light. At least, thats how my leak on my old senator was found.

Gary

[Martin Cox]

Another reason fridges don't usually leak is that the motor driving the compressor is sealed inside the compressor unit and the only connection to the outside world is electrical. There are no moving parts to be sealed. Since at present a car aircon compressor has to be driven from the engine, the input shaft to the compressor has to rotate through a seal and it's not perfect. If this seal is not kept lubricated by running the aircon regularly, it dries out and up goes the leakage rate. So, unfortunately, recharging has to be regarded as a maintenance operation.

Martin Cox

[Mike Smith]

Our local air con guy charges around £50 for a re-gas
Were over in Derby.

Regards
Mike