AC compressor relay(switch in compressor)stops AC operation

moprob99 · Post by **moprob99** » 03 May 2010, 10:15

Volvo V70 1998 non-turbo

The car AC held full charge of gas, but did not engage the clutch on the compressor. I took it to a local foreign car place and they got the AC to come on, it failed 500 miles away when first turned on. (beach HOT). I returned it, and was told it was a switch inside the compressor. Needed new compressor. I declined, since I seldom use AC. I found a really, REALLY GREAT Volvo expert in Rootstown (Ravenna) Ohio www.volvoshopinc.com/ People drive 100's of miles for this guy and his assistant.

Anyhow, he pointed out that the Volvo has multiple safety relays, and it would be quite safe to bypass this relay.

It is simple, just locate the male and female relay wires at the compressor, unplug them, leave the relay in the compressor out, connect the incoming male and female.

(The problem can be checked by a more technical person by applying 12 volts to the output of the firewall mounted ac relay. If the compressor clicks on, it is the internal relay in the compressor. This was how he confirmed the issue)

Initially it did not function. By a miracle of luck, I thought perhaps there was a need to clear some computer decision, so I removed battery power and reset the system.

Full AC now for about a year !!!!! Total part cost = $0, not $350-450, labor =$0, not $300

Matt & Moderator --- > Any safety issues seen with this procedure ???

Post by **jblackburn** » 03 May 2010, 11:05

If you're talking about the switch I think you are, the temperature switch on top of the compressor housing itself, no, there are no problems with overriding it. It's a pretty common failure point, and many people have in fact bypassed this relay without problems.

Free, easy fixes are the best!

moprob99 · Post by **moprob99** » 03 May 2010, 11:22

Is is normal to require the removal of 12V to the system for the by pass to work ??

Thanks

Cosmicbandito · Post by **Cosmicbandito** » 03 May 2010, 13:11

Wow, if this only could be the easy fix for my 1999 V70 AC issues. Would this switch by-pass be a cure for the electromagnetic clutch spacing issue? My AC works great until it gets warm enough outside that I really need it....

Post by **tboothe33** » 03 May 2010, 15:05

Oh boy! I'm crossing my fingers! Will give this a try tonight! If i can get relief from the 90+ degree weather this summer I will be soooooo happy!!!!!!

Post by **jblackburn** » 03 May 2010, 15:43

Wow, if this only could be the easy fix for my 1999 V70 AC issues. Would this switch by-pass be a cure for the electromagnetic clutch spacing issue? My AC works great until it gets warm enough outside that I really need it....

Yes. For more on that:
http://volvospeed.com/vs_forum/index.ph ... lutch-fix/

Do NOT jumper the pressure relay (at the firewall) if you are low on refrigerant, you chance destroying the compressor.

moprob99 · Post by **moprob99** » 04 May 2010, 15:04

tboothe33 wrote:Oh boy! I'm crossing my fingers! Will give this a try tonight! If i can get relief from the 90+ degree weather this summer I will be soooooo happy!!!!!!

This is only a solution for the relay in the compressor failing. The system should be fully functioning and properly otherwise controlled by sensors. Most relays serve a safety purpose, and with AC it's REALLY TRUE. Omitting this one leaves the systems safe from my Volvo expert. (and JAB).

goVolvo · Post by **goVolvo** » 11 Sep 2015, 12:21

Hi, I am looking at AC clutch not engaging problem on my 1998 S70. Looks like I need to check with this. Do you know how hard to access the compressor? Seems it is pretty deep down there and I cannot reach from top. I'd better try from bottom. A picture if any also will be very helpful.

And to apply 12V at the AC relay in main fuse box, do I just need to unplug the relay and jump short the two output pins with a paper clipper? From OP this could verify the problem but Is this adequate to engage the clutch even if the compressor switch is off? I thought the compressor switch is inline on the circuit to clutch.

Thanks a lot.

Post by **Ozark Lee** » 11 Sep 2015, 19:23

The compressor is quite accessible from the bottom after you remove the air guide. The thermal switch isn't really a relay but a simple, single pole, normally closed switch. It is supposed to open when it gets hot and then reset after things cool off but it tends to stick open so most of us just go around it and forget about it. If you have voltage going into it but not coming out of it to the clutch then you have found your problem.

...Lee

goVolvo · Post by **goVolvo** » 11 Sep 2015, 20:22

This is the compressor that looks same in my S70.
So is the switch cable the black one go to the end of compressor? I found the single white harness on the top left corner was disconnected on my car. So I connected it, use a paper clipper shortcut the ac clutch relay. And suddenly it starts working and blow cool air.

But after only a few minutes, before I am too happy, some coolant spilled on engine and there is lot of white steam. I cannot find where it leaks from. Only see some coolant on the low beam and wiring cable between fan and intake manifold.

AC was never working before and I nerver see coolant leak problem. Any idea? Probably I'd start a different thread. I can only think that coolant in radiator is heated up by high pressure refrigerant and overflowed. Wish it is not head gasket suddenly blowed.