Central locking works when it's hot, but only then.

[4th_Saab]

I have a 1992 US Spec 9000S. I've replaced several of the lock motors but my current central locking problem is intermittant. When the car has been sitting in the sun, the central locks work (FWIW, the 1992 cars did not have a keyless remote and one always has to use the key). If the car is moved out of the direct sun, or it cools down a bit, central locking doesn't work.

Any thoughts? (I searched and didn't come up with any help)

Thanks!

[Last_straw]

There is a central locking control unit, under the dashboard, it's a black oblong shape. My central locking started working occasionally and I replced this with one from a scrap yard and it worked fine again.

[4th_Saab]

Thanks!

You have to remove the top of the dash to gain access or find it from underneath?

[Last_straw]

You find it from underneath, for a RHD car it's in the driver's footwell, LHD I don't know . you have to remove the cover and you should find it pretty easily, its held in place with a metal clip.

[winddance]

If that doesn't work just pull the darn unit out and use the key. My quality of life improved greatly when did that.

[4th_Saab]

Winddance...that's how it's behaving now. The '92 US models didn't have a keyless remote so central locking was activated by the key in the driver's door lock only. Right now, the car essentially has manual locks...unless the car has been sitting in the sun then the key locks/unlocks all 5 doors.

I guess the driver's door lock motor is working OK or part of it, because the alarm still arms when the key lock is locked...the system just gets confused from the control unit to the other 4 doors.

[winddance]

I'll clarify: Pulling the central locking control unit out will shut off your power locks so you will then have only manual locks which will only be lockable manually inside the car or with the key. This really gets rid of the long term power lock problems that are bugging almost all saab owners.

[HAL9000]

Originally Posted by 4th_Saab

Any thoughts? (I searched and didn't come up with any help)

Take the box out, remove the box cover, get a soldering iron and resolder each and every component there and you have a perfectly working central locking box until one of those soldering joints cracks again due to crappy printed circuit board laminate used in this cheap imitation of an electronics equipment.

The reason for working in hot but not in cold is bending of the board. In hot weather one of those soldering joints conducts properly but as the board bends in cold weather it does not anymore.

Why are some of the in car electronic devices constructed in such a bad way? Would it really have been so much more expensive to use proper materials like through hole plated FR4 laminate?

[4th_Saab]

Thanks! That's a great idea!!!

On a similar subject...I've always wondered what the thinking was behind the DI cassette. I understand the efficiency of placing it where it is, but I never understood the logic of putting a circuit board loaded with power switching semiconductors on top of a hot engine...

[4th_Saab]

OK...I found the silly ECM, it's essentially toward the firewall above the clutch and brake pedals (obscured by a piece of carpet attached under the dash). It's held in place by a single clip that releases when you pull down on it and then the module unplugs from the wiring harness.

I removed the circuit board from the case and resoldered the pads that weren't covered by a red conformal coating.

Plugging the module back in, the central locking still doesn't work. However, I also had some problems with the linkage in the rear door lock breaking so I was left with in operable central locking and a locked rear door that I couldn't unlock manually.

I removed the housing for the ECM (exposing the circuit board) and then plugged the ECM back in. Manually operating the relays (there are two) caused the doors to lock and unlock.

Could the driver's door lock motor be faulty? Is there a way to check it...continuity between the three leads in the locked or unlocked state or some other way? I'd prefer not to have to keep tearing the door apart if I don't have to...

I have a couple of spares, but I don't know if they're any good either...

Thanks for your continued assistance!!!

[fn0w]

Damn that central locking.... i have had apart all my doors at least once because of it. Earlier i had a problem with a relay plate (ECM) stuck in closed too, and now my rear right lock has started to malfunction

My car is falling to pieces, also because of those damn doors, totally rusting up. About time i look for another car. Don't know if im doing the right thing when I'm looking for a "non-saab"?

[4th_Saab]

Originally Posted by fn0w

.... Don't know if im doing the right thing when I'm looking for a "non-saab"?

Probably...But then again, I always scream "never again" and then end up buying another one...

I'd say you probably got your use out of an '89 though...

[4th_Saab]

Well, I finally fixed it...found a good used ECM and that did the trick.

Thanks to those who posted for their help!