My '03 9-3 Arc has a nasty habit of refusing to turn on the A/C at times. Most of the time a stop, engine shutoff and engine restart fixes it. I usually know within 5 seconds of starting the car if the a/c will cooperate or not. When it turns on, it cools the car very quickly and well. When it refuses to turn on, there is no way to turn it on other than a restart.
I know these compressors are designed to turn on only if the engine cooling fan is on. Well, when the a/c throws its tantrum the fans are both off and this is after driving a while in pretty warm weather, so there's no legit reason for them to take a break. Restart it, watch the fan kick in and enjoy the a/c for the rest of the trip.
So, what's wrong with the fan? It could be the temp sensor. Bumped off the cable and measured about 550 ohms across it. Seemed reasonable (the engine was still warm after a run to the store 1/2-3/4 hrs prior, but not hot). Then again that trip was Ok: fan and a/c both happy together. Seems unlikely that the temp sensor would work intermittently and require reboots. It just isn't that sophisticated a part... Pulled and looked at both fan fuses. They looked fine, which also makes sense - these things rarely cure themselves after blowing. Can't easily get to the relay, without lifting the car, at least not beyond disconnecting and reconnecting it. Thought about trying to get the voltage across the fan that has its power cable come to the side of the relay (BTW, is there no way to disconnect that cable without taking apart half the car's cooling system?), but I'd have to catch it in the act again. Suspecting the ECU, now, or possibly a grounding issue (a few minor things around the interior are either out or flaky, but outside thermometer works consistently, like a champ, though). When it works, both fans are on, when it doesn't, both are off. Any ideas? If I do have to get a new ECU, who can I get to program it (Maryland, US)? Haven't seen many Saab dealerships lately. If it is grounding, where do I start looking? Any usual suspects there? Any other ideas?
Thanks!
I know these compressors are designed to turn on only if the engine cooling fan is on. Well, when the a/c throws its tantrum the fans are both off and this is after driving a while in pretty warm weather, so there's no legit reason for them to take a break. Restart it, watch the fan kick in and enjoy the a/c for the rest of the trip.
So, what's wrong with the fan? It could be the temp sensor. Bumped off the cable and measured about 550 ohms across it. Seemed reasonable (the engine was still warm after a run to the store 1/2-3/4 hrs prior, but not hot). Then again that trip was Ok: fan and a/c both happy together. Seems unlikely that the temp sensor would work intermittently and require reboots. It just isn't that sophisticated a part... Pulled and looked at both fan fuses. They looked fine, which also makes sense - these things rarely cure themselves after blowing. Can't easily get to the relay, without lifting the car, at least not beyond disconnecting and reconnecting it. Thought about trying to get the voltage across the fan that has its power cable come to the side of the relay (BTW, is there no way to disconnect that cable without taking apart half the car's cooling system?), but I'd have to catch it in the act again. Suspecting the ECU, now, or possibly a grounding issue (a few minor things around the interior are either out or flaky, but outside thermometer works consistently, like a champ, though). When it works, both fans are on, when it doesn't, both are off. Any ideas? If I do have to get a new ECU, who can I get to program it (Maryland, US)? Haven't seen many Saab dealerships lately. If it is grounding, where do I start looking? Any usual suspects there? Any other ideas?
Thanks!