SaabCentral Forums banner

1 - 5 of 5 Posts

·
Registered
Joined
·
35 Posts
Discussion Starter #1
It's warming up here in the southern hemisphere, and I'm trying to see what's going on with the A/C on my 900.

Basically, I turn on the A/C and the compressor clutch is not engaging. Initially I though it was just a bad clutch, however I checked for voltage at the little red connector that goes to the compressor, and I'm getting nothing.

I did the test I read about on another thread, where you jump the connectors that go to the pressure switch at the receiver/dryer. When doing that I still wasn't getting any power to the red connector at the compressor. Jumping the wires did start up the cooling fans, however they were working when the pressure switch was connected normally, which indicates to me there is pressure in the system.

When I first got this car the fuse for the A/C compressor was blown, obviously I've since replaced it. Would this be a clue to where the fault is?

The only other culprit I could think of is the relay, however if the relay was faulty, I thought that I wouldn't get the cooling fans come on when I turn on the A/C?

If anyone has any ideas, please let me know.

Thanks.
 

·
Registered
Joined
·
994 Posts
first thing you can do is to check the relay. the saab ac system uses a double throw relay, identical to the fuel pump relay. when my system wasn't working, (for the longest time) it was because it had a wrong style of relay in the holder.
a traditional 5 pin regular relay will NOT do the job, oddly enough.

after that, another issue i had to deal with was that the wires to the clutch cycling switch, that thermostat doo-hicky that looks to see how cold the evaporator is, had come unplugged. easy enough to check. look above ecu and fuel pump relay, it's right there on the bulk head.

after those two easy checks, carry on with fault tracing to find 12v power, starting at the a/c compressor connection working backwards into the system.
 

·
Registered
Joined
·
12,939 Posts
The power from the A/C switch operates the pull-down circuit for the relay. Most electrical problems are in this circuit, which includes the anti-frost (cycling) switch, low-pressure switch, over-temperature switch, and full-throttle switch; some models also have a high-pressure switch.
Half of those switches work on the + side, the other half on the ground side. Find the wiring diagram.
 

·
Registered
Joined
·
994 Posts
one thing that i have noticed is it can help to cut a lot out if you watch what the system is doing.

atleast on my 85' if i turn a/c on, it pre-loads the engine, which causes a running idle tone difference as it putters and sits there.
i found that even if the clutch wasn't working on the compressor that could help narrow a chunk of the circuit.
 
1 - 5 of 5 Posts
Top