Air con compressor not kicking in? Solution:

[Filterlab]

A common problem on the 70 series cars is the compressor not kicking in even though the system is fully pressurised. The air con will work fine for ten minutes and then cut out, it won't come back on until the engine is left to cool down and then restarted.

Anyway, the problem stems from the clutch on the compressor. As the clutch gets worn it requires greater effort to engage and as the wiring to the compressor is very thin the clutch is unable to receive enough supply current to engage. So after nosing around a while, I came across a way of rectifying the problem. It was in a virtually unrelated thread and was a mere passing comment by nobananas on here. Put simply, supplying more current to the compressor clutch will make it work again.

What you'll need to sort it:

4 metres 30amp cable
1 30amp switching relay
1 relay holder
1 30amp fuse
1 fuse holder
2 spade connectors capable of passing 30 amps
2 battery terminal eyelet capable of passing 30 amps
2 pairs of bullet connectors capable of passing 30 amps
zip ties (quite a few)

Firstly locate the air con compressor. Looking from the front of the engine it's on the left hand side directly underneath the alternator. It's a bit of a bugger to reach as there is a maze of pipes and wires directly above, however the connections can be made from underneath the car. On the compressor body there are two clips both of which hold connectors. The horizontal one is the ground and doesn't need to be touched. The vertical one is the supply (white and barrel shaped with a double clip) and this is the connection that is to be broken. Unclip this connector and cut off the plug. Label or remember which wire comes from the loom and which connects to the compressor body.

You will have to jack up the car to get to these cables for the purpose of rewiring. Once it's up in the air, remove the front splash guard, there's a bolt at each end to undo, a sensor on the right hand side of the car to remove and then the guard should unclip fairly easily. Using the 2 pairs of bullet connectors, connect each cable to approximately 1.5 metres of your 30amp cable and feed the cable up to the loom in the headlight area and along the bonnet release cable ducting over to the battery corner of the bonnet. Loosely zip tie as you go.

The first connection to make is from the wire which travels to the compressor from the dashboard loom. This becomes the switching supply for the relay and is connected to pin 86 (using the relay holder and crimping the cable into the pin receptacle).

The second connection will be the 30amp supply to the compressor and this is connected to pin 87.

With those two in place the next connection is from the positive terminal of the battery. As the relay is positioned right next to the battery you'll only need two pieces of cable 20cm in length. On one piece crimp the battery eyelet at one end and a spade terminal on the other. On the second piece crimp a spade terminal at one end and the other end is connected to pin 30 on the relay. Connect each spade terminal to the fuse holder, pop the fuse into place and connect the eyelet to the positive battery terminal.

Lastly connect pin 85 to a grounding point but preferably not the battery, there's lots of bolts near the corner of the bonnet so choose any one of those that will not compromise the wire and cause it to break.

The connections are now made so pop in the relay and the fuse, all that's left to do is secure everything in place with zip ties. I used a long zip tie around the air intake to secure the relay holder and fuse holder. Start the engine, if you've done everything correctly then the compressor should click in and out merrily. If you've made an error then the fuse will blow and save your car for you.

Thanks to nobananas for this advice, hopefully this post will help someone stay cool and calm as they enjoy their Volvo.

Relay diagram:

[Rufe]

looks like a good fix there mate, and not too complicated for the home Diyer

[Filterlab]

Well I managed it!

Cheers.

[snoop69]

Nice tip bud but how about a cheap fix (other than a shorter belt) for a compressor that starts to smoke & threatens to catch light after 10mins?

[Filterlab]

[snoop69]

I had to throw 3 kettles worth of water over it.

Smoke was coming from under the wheel arch,between the wing & bonnet
& around the headlight!!!

[Filterlab]

Jeez! New compressor I think.

[snoop69]

Jeez! New compressor I think.

Was thinking the same to be honest.

Luckily its not my car & i think the owner is going to fit a non-ac
drive belt for now.

[Engineer]

You might need that bucket of water as your clutch coil pack should only be drawing around 3-4 amps max, did you check your AC clutch clearance (up to 0.5mm IIRC should be ok) as it is adjustable for wear by shimming

[nobananas]

Nice write up mate, couldn't have done better myself. As for re-shimming it is possible but very hard to do with the pump on the car, I tried to re-shim my old compressor off the vehicle and I still couldn't release the plate from the clutch assembly without damaging it so doing it with the pump on the car is very tricky !

[Filterlab]

Cheers

[V70R999]

Might have to try that with the V70R. New owner is waiting for me to get it sorted before collecting it. Mine comes on for only about 5 seconds then switches off and some of the lights such as recirc flash. Going to drop her down to the garage to get it fixed tues but might have a try today. Cheers

[Filterlab]

No problem mate. If you need a hand give me a shout.

[Neil]

Might have to try that with the V70R. New owner is waiting for me to get it sorted before collecting it. Mine comes on for only about 5 seconds then switches off and some of the lights such as recirc flash. Going to drop her down to the garage to get it fixed tues but might have a try today. Cheers

Sounds more like low gas pressure.

Symptoms of the clutch dropping out or not engaging, are the A/C working fine for, say, around 15 minutes. Then after that point, no cold air.

[V70R999]

Cheers Neil, obviously don't want to spend any money on a car I've just sold.
When I start the car the fan kicks in for only a few seconds then switches off. Then for a while there is nothing (except for some of the climate control lights flashing amber). A while later I might switch on the fan ( moving the slider from 0 ) and again it only comes on for a few seconds.