AirCon runs cold but fails after 5-10 mins - 2000V70

Furball · Post by **Furball** » 15 Apr 2007, 16:56

Hi all

First post on this forum, hope someone can help. At the last service my dealer purged and recharged the aircon on our V70 as it wasn't working well. Since then it has only come on and blown cold for 5-10 mins before cutting out. Doesn't usually restart on the same journey.

The dealer has looked at it again, claimed no leaks and suggested replacing the electronic clutch as it seemed 'a bit weak' but didn't promise that this would cure the problem.

I've done a bit of looking round and I can see that there are other possible culprits (pressure switches, relay, sensors) but can't find any info of how to test or diagnose in detail. I don't have any fault lights showing by the way.

Can anyone offer advice before I have to put my trust and cheque book back in the hands of the dealer?

Many thanks
Gareth

Post by **fiore67** » 15 Apr 2007, 17:20

Hey Gareth,

When you say it fails after 10 mins do you mean the compressor stops running.

Furball · Post by **Furball** » 16 Apr 2007, 14:08

Sorry, I meant that the cold air stops coming through the vents after 5-10 mins. After this the fan just blows through air at the outside temperature i.e. no cooling going on.

Is there an easy (visual or multi-meter test) way to check if the compressor is running or if the mag clutch is engaged at the point when the cold air gives up?

I should add that the car is a 2000 V70 Classic model, has done 94k miles and was UK supplied and spec'd. It has had regular scheduled service work but as far as I can tell no other work on the aircon system since it was new.

Gareth

Post by **MadeInJapan** » 16 Apr 2007, 17:36

Open the hood and do all of this at idle...you will hear the compressor go on and off...if it goes off and stays off, then you have an issue....also, there might not be enough gas (a leak?) in the system, although I know it was filled up...best is to check the pressure from the low port (the one with the screw off cap) with the car running and compressor engaging.

Furball · Post by **Furball** » 05 May 2007, 03:28

Hello again. Looked at the compressor carefully and realised that you can see the end plate turning when the compressor engages. Didn't spot this before - doh!

Looking for more suggestions now. Have worked from the 850 manual as the V70 cliamate looks pretty similar.

Have tried starting the car with AC on, recirc on & fan at max and the compressor doesn't kick in.

Going from the manual, the wiring diagrams and Keith Potter's very informative air con essay have tried:

1. unplug low pressure switch, start engine - compressor doesn't engage

2. unplug the high pressure switch start engine - compressor doesn't engage

3. bridge the air con relay start engine - compressor doesn't engage

The only other thing I can think to try is to power the compressor directly. The wiring diagram suggests I could bridge power to the output from the low pressure switch and this would go directly to the compressor with no other switches or controls in the way. Does this sound right?

I guess if the compressor still doesn't engage with direct power then the mag clutch must be the problem.

Anyone have any other thoughts?

Thanks
Gareth

Post by **Ozark Lee** » 05 May 2007, 06:19

You can power the compressor directly but it is much easier to simply place a wire in the connector to jumper the low pressure switch. Proceed with caution as, if the system pressure is indeed low, you could ultimately damage the compressor - back to the cheque book but a larger number on the cheque.

If the system still cuts out it could be that your system is over charged or there is something blocking the R-134A flow in the system. If, after jumpering the low pressure switch, the system continues to cut out and further assuming that the compressor has not blown up before, I would concentrate on the receiver / drier as the likely culprit.

I had to change my receiver / drier but it was due to condensation ultimately rusting it out and causing a leak.

...Lee

Furball · Post by **Furball** » 07 May 2007, 14:34

Thanks for that Lee, tried jumpering the low pressure switch and the compressor starts / stops on the button. Great stuff! First time I've seen it working and at least I know the mag clutch works when cold. Didn't run it for long, need to get the gas pressure tested now!

Another question - on the 850 wiring diagram the compressor is powered directly from the low pressure switch and nowhere else i.e. if the pressure is low and the switch trips the compressor won't get power from anywhere else. Anyone have a diagram to confirm that the 2000 V70 is the same setup? (it looks like it is and logical to avoid compressor damage!)

If so the problem is most likely low pressure (leak) or a duff low pressure switch? Anyone else ever had a duff pressostat?

Thanks
Gareth

Post by **Ozark Lee** » 07 May 2007, 15:03

The chances are very good that the system pressure actually is low. The pressure switches have historically not been a problem but there is a first time for everything.

I'm not sure where you are and thus I am not sure of your local regulations but virtually all of the auto parts stores in the US sell R-134A recharge kits over the counter with no certification required.

I have a set of Air Conditioning gauges so I just but the cheap cans whenever I need to add refrigerant but I have seen some recharge kits that come with a gauge on the can. I've also seen recharge kits that claim to stop leaks, they usually don't work but it actually did work on my Jeep where the problem was a leaky schrader valve.

...Lee

Post by **luketrash** » 07 May 2007, 16:01

It could also be too high.

When it's off, I get about 100psi on the low end, and it drops to about 35psi when the compressor is running. This is on my 94 850 with working AC.

For what it's worth.

Furball · Post by **Furball** » 15 May 2007, 06:47

A few more checks done now.

Low side reads 60 psi without compressor running.

Tried jumpering pressostat during pressure test but compressor wouldn't start. Checked pressostat switch socket and steady 12v going through to compressor but no start.

Tried again after engine had cooled down and compressor started and ran for 3-4 mins until I switched A/C off and tried again. Compressor would not restart.

Could this problem be related to engine temp and the compressor warming up? Sure I read something about the mag clutch tolerance changing when it gets warm but can't find it again now.

If I route 12v directly to the compressor mag clutch feed could I check for it engaging without running the engine? i.e. would it damage aything by trying this?

Any more ideas MUCH appreciated before I have to drag the damn thing back to Volvo.