A/C Compressor Engagement Band-Aid or "fix"

thanks for this! gonna try it and see if it works.

So I have a 2008 Saab. The small black relay for #2 on mine is the fuel pump relay. is it different with the earlier models of Saab?

the fuel pump relay is located behind the passenger side kick panel..

just looked in my 04 om says fuse#2 is fuel pump R2 is a/c compressor..Can't see saab/gm changing that,as it would cost $$$$ to make a new loom..

In anticipation of the pictures failing because of photobucket behaving badly, here's the original post, redone with a different photo hosting.

I'm sure I'm not the only one with a chronic problem of the ECU disengaging the relay and turning the air conditioning off. Here's a band-aid technique I rigged up on my car (04 Aero) that keeps the a/c compressor engaged when the engine is running.

Do understand that the compressor does not ever cycle when rigged up this way. It is constantly engaged when the engine is running. It does disengage as soon as the engine is shut off.

This does not fix the underlying problem with whatever is causing the ECU to drop the grounding signal to the a/c compressor relay.

But, if you want or need air conditioning, this does indeed "get er done".

You need about 10" of fine wire. The current load is tiny, so it doesn't need much capacity. You also want it thin so it fits into the blade sockets of the relays. In my case, I used very fine stainless steel wire. Copper would work better, but this does just fine. Mine is bare, so I have a little care with where it lays.

Pull the a/c compressor relay, #2 as I recall. It's the little black one. Connect the fine wire to pin 85. This is the ground side of the relay coil. I just poked the wire through the hole and bent it over.


Pull the main ecu relay, #4 as I recall. It's the red one on the right. Connect the other end of the fine wire to its pin 85. This is the ground side of the relay coil here too. Again, poke the wire through the hole and bent over.


Plug the relays back in. Here's mine, all plugged in with the little wire shown.


And here's the wire more neatly tucked away.


This works by jumpering the ground for the a/c compressor relay to the ECU relay ground. Basically, as long as the engine is on, the relays are both grounded. So the engine runs and the a/c compressor is engaged.

It works. That's the main thing. I've been running mine this way for about a month now as I keep trying to diagnose and fix the P0687 code that keeps cutting my a/c compressor out.

Hopefully this will help keep some of you cooler and more comfortable in the summer heat.

Did you ever repair the fan relay issue causing 1 or more of your fan speeds and compressor not to work?

Thanks for the band aid fix. It worked for me too. I used a thin wire and my AC is now blowing ice cold air.
has anyone figured out how to fix the issue though? I don’t really want my Compressor to be always on. Thank you so much!

Thanks for this!! My a/c is out for this hot summer, even after replacing the ecu. Just did the hotwire and went for my first cool ride in weeks.

That was short lived - cut out again after about 15 minutes. Hmmmmm.

How hot is it getting? There's overheating protection on the clutch.