Air con help please

[Quicksilver]

My air con has suddenly stopped working after the car has been sat for two weeks. With the engine running I can hear the usual clicks but the pumps not engaging. Are there some usual things to check?.

Cheers
Steve

[pookie]

Check the air con low pressure switch at the back of the engine bay, just bridge it out and see what happens. Let us know what happens and I'll take you to the next stage if necessary.

Salut!

Pookie

[Quicksilver]

I've put a gauge on and system has pressure, I've bridged the low pressure switch at the rear of the engine compartment as you asked and the pump now kicks in!.

[pookie]

Sorry for tardy reply. Renew the switch. This should cure the problem. If not, get the system recharged.

Salut!

Pookie

[pookie]

I'll start again. The low pressure switch prevents the compressor from working if the system pressure is too low. So either the switch is faulty or the pressure is too low. To change the switch you'll have to de-pressurize the system first. When the switch is changed then do an A/C recharge.

Salut!

Pookie

[Quicksilver]

Cheers Pookie, I've got one of the gauges that comes with the top up kits and it says the system has pressure of 24psi (lower end of the blue normal area) and when I byass the pressue switch the pressure rises, does this point to the switch being faulty?.

Thanks in advance
Steve

[pookie]

To be honest I'm not sure. I can't get any technical info. that deals with pressures in the A/C system only weights of refridgerent. Sorry. However as by passing the switch makes the compressor work O.K. I 'd change the switch.

Salut!

Pookie

[Quicksilver]

Thanks again Pookie, are these swiches generic or do i need to go to Volvo for it?.

Steve.

[pookie]

I'd go genuine Volvo. Speak to Rufe.

Salut!

Pookie

[Flatout Phil]

My recommendation is to get a specialist (there are some mobile ones) to take a look. If your pressure is low, and quite honestly, it is very low, I would have the system serviced - and in all likelihood, have some sealant put in the system. If that is done, it is usual to replace the accumulator (a tank thing to the off-side of the radiator). I have had this job done on two 850s, the price is about £170 - more than a KwikFit regas but on 850 the aircon is shaky, and by using this method you can (if you catch it in time) fend off problems like a leaking matrix under the dash which is a TOTAL pain in the harris to fix.
A regas and a service are VERY different - and having attempted to use three different KwikFit branches for regasses, they do seem very undertrained by comparison to my mobile bloke. Luckily, they could never fit me in!
As with Pookie, I agree that the problem is low gas, not sure about the switch - he knows more about that than I do. My hunch is a leak, because there are few 850 that seem to hold their gas for more than about two years. And act sooner rather than later.

[AndysR]

What he said ^^^^

On mine when I got the car the air con worked well, then over time I could feel whilst driving that the compressor would cut in and out more and more frequently until one day it stopped cutting in. I bridged the switch as described to bypass the system safety feature and the compressor cut in. This will tell you that either the system is low on pressure or the switch has failed and you must only do this briefly as you can damage the compressor due to the possibility that the gas level is low. Once you have confirmed that the compressor cuts in you could get the gas level checked and if low topped up and checked for leaks, if it's ok then the switch has failed and will need replacing.

Going further into what Phil describes.
I've had the evapourator renewed on mine, it's a dash out job and not cheap. I also had the receiver drier replaced, which is the air conditioning system filter, at the same time as is always advised if the system has been subject to a leak. The major killer of the evapourators on the 850's is the lack of a standard fit pollen filter. This allows small leaves and pollen to collect on the evapourator this then decomposes and traps moisture this corrodes the evapourator and causes it to leak, that's what caused the failure of mine and needless to say I now have a pollen filter. Luckily for you I think all the 70 series cars had a filter fitted as standard, that said there is nothing stopping someone removing it and not replacing it so worth checking or yours could end up looking like my original on the left....



I also had the low pressure switch and compressor renewed at the same time, I have poly torque mounts and when driving I can't even feel the compressor cutting in and out now the only way I know the compressor is cycling is the engine note changes.

[Flatout Phil]

What he said ^^^^

On mine when I got the car the air con worked well, then over time I could feel whilst driving that the compressor would cut in and out more and more frequently until one day it stopped cutting in. I bridged the switch as described to bypass the system safety feature and the compressor cut in. This will tell you that either the system is low on pressure or the switch has failed and you must only do this briefly as you can damage the compressor due to the possibility that the gas level is low. Once you have confirmed that the compressor cuts in you could get the gas level checked and if low topped up and checked for leaks, if it's ok then the switch has failed and will need replacing.

Going further into what Phil describes.
I've had the evapourator renewed on mine, it's a dash out job and not cheap. I also had the receiver drier replaced, which is the air conditioning system filter, at the same time as is always advised if the system has been subject to a leak. The major killer of the evapourators on the 850's is the lack of a standard fit pollen filter. This allows small leaves and pollen to collect on the evapourator this then decomposes and traps moisture this corrodes the evapourator and causes it to leak, that's what caused the failure of mine and needless to say I now have a pollen filter. Luckily for you I think all the 70 series cars had a filter fitted as standard, that said there is nothing stopping someone removing it and not replacing it so worth checking or yours could end up looking like my original on the left....



I also had the low pressure switch and compressor renewed at the same time, I have poly torque mounts and when driving I can't even feel the compressor cutting in and out now the only way I know the compressor is cycling is the engine note changes.

How do you get at the pollen filter Andy?

[AndysR]

How do you get at the pollen filter Andy?

Pollen filter is under the scuttle panel trim on the passenger side of the car. All you need to do is unscrew the passenger side of the trim and then lift it up it's flexible enough to not have to worry about completely removing the trim.

[Quicksilver]

Thanks for all replies, I'll get a local mobile guy in to look at it.

Steve

[Quicksilver]

All sorted, service/recharge, only 100kg of gas in the system should be 750kg!!, leak tested all good, result.

thanks for all the replies.

[AndysR]

Fingers crossed it's not got any minor leaks and it holds it's gas, nice to see it was a simple fix.