Aircon cycling

[ether]

Hello all. I picked up a 2004 XC90 last week and am loving it so far. However the climate control started playing up yesterday and I was wondering if anyone had any ideas about what might have gone wrong...

After driving for 30mins with the AC on auto the compressor seemed to stop working (noticed warm/damp smelling air coming through the vents) and the cabin started to warm up. I left the windows shut to see what would happen and after 5mins the fans started to speed up (presumably because of the growing difference between actual temp and desired temp).

10 minutes later and the heat was too much so I opened the window. Fan speed remained high. Turned the AC and blowers off after another 5mins (by turning the fan dial fully anti clockwise) and then, after another 5mins hit the auto button on the AC and started to get cold air again.

Compressor cut out again after a further 10mins so turned the system off for 5 minutes and it was OK again. Repeated this about 5 times until I got home.

There were no error messages displayed in the car and I haven't tried it again today. It might be my imagination but the AC seemed to stay on longer as the outside temp dropped - it didn't cut out at all for the last 20mins of my journey (arrived home at about 7pm).

Any ideas?

[Rockhopper]

You've not had an a/c re-charge recently have you?

There's a high pressure cut-out for the compressor which would fit those symptoms - I had a very similar experience after I had to have an a/c service when one of the compressor hoses sprang a leak (v bad routing design that meant hose rubs on plastic housing).

Anyway, I replaced the hose and then a/c engineer came out to flush, recharge and pressure test. All of his a/c 'bibles' for XC90 out with a 1kg recharge weight for refrigerant- which was duly applied. A week of running and I got your symptoms, a/c would work fine then cut out, coming on again after a while.

Turns out the recharge weight is actually 0.7kg (NB for cars with 3rd row aircon it is indeed 1kg). Engineer recharged with correct weight and hey presto it was back to normal. The high pressure side of the a/c was too high and hence sensor cut the compressor off to alleviate.

Worth checking out with a decent a/c engineer that actually weighs (accurately!) the refrigerant volume that is recharged to your system.

[ether]

Appreciate the info. Tbh, I only picked the car up a week back and am not really sure what it's had done in the past. It doesn't have the 3rd row AC so I suppose it's possible. It's got a full service history and only 1 previous owner that seems to have used the same dealer throughout. Maybe I can ask them to print the history out for me. Would they usually do that?

I have only done 5 minute journeys since posting and it's been fine on those. Will hopefully do a longer trip this weekend to test it out again.

It's been with my local mechanic today (high mileage and a few suspected issues so I wanted him to check it over). He said it looks mostly good but needs a rear wheel bearing, there's play in the steering rack (he said it may just be a rack end) and the rear wheel drive isn't working (I knew about the bearing and rwd).

Have read the extensive thread on the rwd issue and am hoping it's just the splined sleeve that needs replacing. My mechanic's not a dealer or even a Volvo specialist - do you think he'd be OK doing that?

Oh, one other thing I've noticed - whenever I turn off the ignition I get 3 beeps and a message saying that the 12V rear outlet is in use...nothing's plugged in to either of the rear outlets so assume this is another fault. Anyone seen this before?

Cracking forum by the way...I've read through a lot of the archive and it pretty much convinced me to take the plunge with the XC90. Was expecting to spend a bit to put the initial issues right and am loving the car so far...fingers crossed that I'll still be loving it in a year's time :-)

[ether]

The AC is still playing up so I've just dropped it off with the mechanic. He's going to check how much refrigerant is in there.

I stumbled on a few threads about the clutch gap on the compressor causing intermittent AC. It doesn't sound like exactly my problem but the clutch on the compressor doesn't seem quite right:

When the AC is working normally the clutch is engaged and I can see it is tight up against the compressor (there is no gap between it and the wheel that the belt goes round on the end of the compressor). I can just hear the compressor working above the sound of the engine and get nice cold air from the vents (about 6 degrees, which is what vadis says it should be).

With the AC forced on permanent cooling and the fan speed at about 50% the clutch seemed to be engaging/disengaging quite frequently (approx 8s on, 5s off). With the fan speed set to max, the cycle changed to 45s on, 5s off.

When the clutch disengages, there is a 2-3mm gap between the clutch and the compressor body (I don't know what the gap is between the actual clutch plate, this is just what I can see from looking into the engine bay).

After about 20 minutes of being on perm cooling, the AC stops working. I get no cold air and I see that the clutch is disengaged but the gap is different than before - now it is only around 0.5mm from the compressor.

When it gets in this state and the fan is turned off and on again, I do see the clutch move very slightly but not enough to engage...it almost looks stuck.

Leave the AC off for 5mins and turn it back on again and the clutch then engages properly and I get nice cold air again. The clutch then goes to engaging/disengaging (8s/5s or 45s/5s depending on fan speed) and the air stays cold. After 5-10mins the clutch gets stuck with this 0.5mm gap and the air goes warm.

Does anyone have an idea of what this could be? I'm assuming it's not the shims in the clutch because it seems to get stuck closer to the compressor, not further away (the threads I read regarding the clutch spacing said it failed because the gap got too wide).

Oh, I found out what was causing the '12v rear outlet in use' message - the previous owner had fitted a tracker and spliced into the 12v rear outlet for power...so the car was telling the truth after all! Some older models (I think 04 and earlier) have a shunt (RSH3) that is used to measure current in the circuit...I imagine you could also get the message if this went bad.

Cheers.

[sumomeister]

This might sound like a daft question, but how can you tell if you have the 3rd row AirCon?

[GJB]

A switch on the front panel and a seperate fan control in rear alongside third row on nearside