Hi!

I have a 2010 Volvo XC70 3.2. I bought it 6 months ago and the AC worked at the time. After some strange turn of events the AC stopped working. It was a really hot day and I was on a near empty tank. At some point the engine warning light came on and reported that the engine was overheating and that I need to stop the car. I did and the AC has not worked since then.

Anyhow, I figured I wouldn't need to worry until springtime now. I have tested a few of the components:

1. The fuse is fine (tested visually and also seeing continuity with a multimeter
2. I tried shorting the low pressure switch. There are three terminals in this one, shorting the farthest ones seem to engage the AC clutch but then the engine stalls
3. The AC clutch turns freely by hand, pushing it in with a screwdriver while the car is running doesn't cause it to engage
4. I tested the leads going into the compressor and this one has two wires in, one wire is at 2.4V and the other wire is at 12V.
5. I checked if it would take some R-134a and it seems as though it's around 70 psi. Although using low end gauge and while the compressor is off.
6. I haven't checked the relay yet

Looking for any helpful pointers and hoping I don't need an entirely new compressor

 

If the thermostat breaks (common on that engine) and the engine runs slightly hotter than normal - the compressor won't turn on. Did you ever solve the overheating? Many things will keep power from going to the compressor. Engine, evaporator and outside temp are 3 of them.

A compatible scan tool will be able to manually activate the ac button, check temps to help you diagnose why your system is not coming on.

Also the compressor used on that engine is a variable displacement type. Google volvo variable displacement valve for info - (many valves have been replaced to solve ac cooling problems)

 

Thanks! I managed to get Vida running and realized I was testing the valve wire on the compressor and not the clutch wire. I was thinking of doing more testing but given your answer I'm thinking might be best to get Volvo to test the sensors.

I never solved the overheating. It just seemed to not happen again. I thought maybe because it was abnormally hot on that day that it happened in the first place. But winter also came.

I tried testing with a standard ODBII and nothing came up as faulty.

 

The basic OBD testers - are for emission related codes only.

If you have a bad displacement valve - a dealer will probably want to replace the compressor.

 

Makes sense, thanks

Do you have any recommendations for anything more I can diagnose myself? I'm trying to avoid a $1000 bill and I've done my own AC clutch replacement in the past, successfully.

 

Sure - the ac clutch relay is grounded by the ECM (applies power to the compressor if all other parameters are met). You could use a jumper wire to send power directly to the compressor (at the relay plug) to verify the clutch and compressor works - (and if the big pipe gets cold, meaning there's freon in it)

You could use your VIDA to see if there are any codes related to your problem in any control unit and examine temp sensor signals (engine, outside and evap)

Wiring diagrams (if they didn't come with your VIDA) can be found at volvodiag.com.

 

Ok so I shorted pins 3 and 5 and the clutch didn't engage. I think I heard a click but I had to juggle starting the car and putting it in and out of acc mode. I also tried to push the clutch in manually and it didn't seem to engage either while the pins were shorted.

I also managed to get to the compressor power and I'm seeing 13.5 V.

I took note of the following pin reads:

1 - 2.5V
2 - 12.5V
3 - 12.5V
5 - 0V

It's starting to look more like the clutch, or the compressor is toast. I am also planning on asking if Volvo can diagnose the sensors. I have Vida but I don't have DiCE. I'm also fairly new to Volvo, and amazed that these tools exist, but I understand that DiCE is needed to read from the car, is that correct?

 

I am looking at the diagram. Part # 7/8 labelled P is the low pressure sensor. Yesterday when I connected two of the three wires (BN and GY-BN), the clutch engaged and the engine stalled. I can't tell what the wires are yet, except that only one was 12V and the others were 0. Connecting the BN and GY-BN caused the clutch to engage and the engine to stall.

 

I brought the car to Volvo, they ran a vacuum test and cycled the freon. The system doesn't leak but the freon was low. They didn't end up doing any other diagnostics and only suggested I replace the compressor.

I don't want to do that, is there anything else I can do on my own? I just tried bridging the relay again and pushing the clutch in, neither worked.

 

If the system is low, there is a leak. Freon is put in by weight. The only way to accurately tell if it's low - is to weigh the freon in the system. Modern recharging machines do that easily - it's weighed as the freon is taken out. I don't think they did that. (evacuated and recharged the system)

Bridging the relay. - OK - Start car, turn ac on auto, use a jumper on the relay socket to send power to the clutch. Does the clutch engage? Is there 12 volts on the correct terminal (coming from the good fuse?) Are you sure the inside part of the clutch is not turning when it's supposed to?

If you have a good compressor fuse (11b/32) and the wiring is intact going to the compressor clutch (you can check for 12v at the clutch connector) - the clutch should engage.

Or with engine off - send power to clutch (with a jumper wire) - there will be a magnetic field generated by the electromagnet - hold a wrench on the front the compressor - magnetic field present?

One way those (6cyl) clutches fail - there is a "dampening ring" that can come loose between the clutch plates - the broken parts jam and prevent the clutch from engaging. Picture of broken "dampening ring" out of place below. If that's the problem - simply remove the ring and reinstall the outer clutch plate. (or replace the clutch with a new one)

 

Thanks for all of the detail. So I checked everything in detail again -- there's power to the compressor clutch but no magnetic field. So I started looking for a new clutch, then realized they're just as much as a new compressor right now so I figure I'll just replace it all at once.

 

About $300 for a clutch - (possible part number below) Takes me about an hour to replace one.

 

That looks like a good deal. I'm in Canada and found a new non-OEM compressor for $310. I am thinking that I could also get a new valve at the same time for about the same price after I pay duties.

How do you manage to change the clutch in an hour? As far as I can tell I need to remove the following to get enough clearance:

- Air filter assembly (plus air intake)
- Battery
- Loosen the belt
- Compressor bolts

to the compressor

 

The displacement valve is part of a new compressor.