V70 Air Conditioning Problem

[bestservedchilled]

Hi, newbie here! Just the time of year to get an air con problem in my 1997 V70

What is good:
Aircon recharged and OK
Compressor clutch OK
Climate control center works as normal
Everything seems to be working....

What is not good:
The compressor is not being switched on.

So far, I have determined the following:
If I provide power to the compressor relay in the Main Fuse box, the compressor comes on and works fine. Even though the climate conrol centre is showing that the A/C is operating, the signal does not seem to be getting to the relay.

I took the car to the Volvo dealer who ran the diags - they showed the fan blower was faulty - but it is working as it always has, fast, slow and auto.

I don't have a circuit diagram to trace the cabling back from the relay, so I'm wondering if I've jumped to the wrong conclusion about the signal to the relay.

Anyone experienced this problem - and better still, found the solution?

Looking forward to being flooded with replies.....

David
Cornwall

[bestservedchilled]

Just been to Volvo to confirm that it's not the relay and it's not the low gas switch either. They are just as confused as I am. Looking at the wiring diagram (I sneaked a quick one) there appears to be a link to the ECU (Please don't let it be that..... ).

I'll update as items are eliminated.

Cheers
David in steaming hot Cornwall

ps. I have temporarily bypassed the system and have the compressor working - the Volvo man seemed impressed by my ingenuity.....

[MadeInJapan]

I would suspect the clutch gap on the compressor has gotten too large. Should be about .025inches...but after years of use it can grow to about .04inches...you can measure with a feeler gauge. From under the car with the plastic liner pulled up and clamped you can reach it without evacuating your system. Pull a shim out of the clutch gap and see if you can reduce the gap to close to the original as you can. I've read this over and over on the brickboard for the same symptoms you're describing...don't know why the dealer doesn't know this issue and its fix.

[bestservedchilled]

Hi, many thanks for taking the time to reply.

If the clutch gap was too large, how come it engages when I bypass the relay? When I check for a signal at the relay, there's nothing there when the A/C is turned on. This suggests that there's something wrong between the A/C 'On' button and the relay as everything alse seems to function correctly.

Still hunting.......

David in even steamier Cornwall.

[MadeInJapan]

I may be wrong but my understanding is that the clutch has a loop signal back to the relay, thus gap too big= no signal to the relay to engage the A/C compressor. Someone correct me if I'm wrong. But if I'm right, then hopefully this answers your question.

[SimLyons]

Another new guy looking for help with AC on 1997 855-R. Last fall AC stopped working intermittantly. After sitting overnight it seemd OK for a while. Sometimes after turning it off for a while it would cycle on but weak "cool air". It was fully recharged in June last year. Now with warm weather coming back I need to figure it out. at present nothing at all comes out of the AC. I also can't hear or feel the "click" of the compressor cycling on/off, or drop in RPM. I am guessing the clutch is not engaging and from all the bread clip posts that might be the fix??? Or the relay? (Is the relay identified in the fuse housing?)

Thanks for any/all help! Sim

[JRL]

[When was and was the evaporator ever replaced?
You should know these go bad every 6-8 years or so!
Recharge again, I'll bet you will be OK.
When you have to charge it every 2 months or less that will be the time for a new one

[jblackburn]

If the pressure in the system is below 25 PSI, the compressor won't even switch on.

You can have it refilled, or you can do it yourself. Since yours is so low, I'd suggest having it evacuated and refilled by a shop. Once you need to top it off again, you can try some of this:

https://www.matthewsvolvosite.com/forums ... =4&t=30434

I've had it going for over a year, and it seems to have stopped my leaky evaporator in its tracks - it went through all of last summer and this winter without being used, and was still cold when I used it today!

I suppose that depends how fast yours leaks back out. Mine needed a recharge every 2-3 weeks and it was seriously starting to get on my nerves.

[SimLyons]

It's too cold (ambient) to do anything with recharging. I did hook up the EZ Chill (with gauge) and it was in the yellow (near zero pressure), but the engine was not running. The ambient in the engine compartment was probably close to 70 deg F, though. I'll wait for some decent warm weather and do the whole thing.

Thanks for the tips! Will get back if this doesn't help.