Crawls Backward (When Alarmed)

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SAAB c900 Power Window Switch Pack Maintenance

So the Regal tenor guitar is still in progress.  In the interim, I got a bit sidetracked with SAABmarine #2 (the convertible).

I have had complaints from passengers that the passenger side power window switch seemed "sticky."  So I took the switch pack out to investigate.

The interior light switch is also a bit wonky, so I took that out too.  You can see there is some corrosion on one of the contacts.

On later model (MY91-93 all cars and 94 convertible) 900s, the power window switch assembly is a "pack," meaning there are not separate switches as with the earlier cars.

To service the pack, the case just separates.  If you use some small-bladed screwdrivers carefully, it comes apart easily.

This is actually the bottom of the pack.  I wasn't sure how it was all designed, so I took the bottom cover off.  As it transpires, that's not necessary.  The other seam you may see in the picture is for the top half.

If you take the bottom half off, you'll be able to get to the circuit board for the "automatic" down mechanism.  The big coils on the ends are the relays that engage until the windows are lowered.

The terminals on the right side are the contacts that hook up with the connector in the car.

As I say, I unnecessarily, unknowingly took the bottom half off, but now you know what it looks like!

If you want to clean the contacts (as I did), take off the top half.  You can see how I used the screwdriver method again to get the cover up off the mounting tabs.

This is what you'll see with the top cover off.

The switches are just 'V' shaped brass contacts that swivel in order to touch the proper contact point when the switch buttons are pressed.  The switch buttons have prongs that contact the contacts to activate them.

There are a number of variants on the switch pack depending on the actual car - 3-door, 3-door with sunroof, 4-door, 4-door with sunroof, or convertible.  Hence the unused contacts on the convertible switch.

Closeup of the switches.  You can see they do have some corrosion on them.  The red arrow points to one of the contacts for the front windows - the switch contact swivels when the button is depressed, makes contact with that tab, and the automatic down circuit is engaged.

Note also that the 2 swiveling contacts are slightly different than the others on the board.   You'll need to know this when you put it back together.

I took off all of the switch contacts and gave them a good cleaning with Deoxit.  I also cleaned the contact points on the switch pack itself, including the contacts that plug into the connector on the car.

You can see how the contacts can just swivel in place due to their 'V' shape.'

Nice and shiny.

Now we just put it all back together in reverse order of disassembly.

I also cleaned up the top/switch button panel.

Here's the rejuvenated switch pack and the interior light switch ready to back in the car.

The switches all work smoothly.

Now for the bad part.

When I put the pack back into the car, the rear windows worked fine.  But the fronts didn't work at all!

I took the pack apart and checked that everything was assembled correctly.  It was.  I also borrowed another switch pack and the front windows didn't work with that one either.

Hmmm.  Diagnosis mode.

Long story short, I just started checking the circuit itself. The fuse for the front was fine.

So I consulted the schematic.  The front and rear windows are on different circuits.  Since the rear worked, something was not right with the fronts.  The fuse for the front was fine.  Then I started checking voltage in the connector in the car.

Here's the connector in the center console.  There are three terminals - 10, and 11, that deliver the B+ (positive) to the front (#11) and rear (#10) windows.  Terminal 12 is the ground.  (See the notes on the picture).

With the ignition on, and the voltmeter between terminals 10 and 12, I had voltage.  Between 11 and 12, I did not.

The cable under the connector makes a bunch of tight turns and my guess is there is a break somewhere that cropped up when I took the pack out of the car, since I moved the cable in the process.

I will trace (and probably rewire) the lead to terminal 11 in the future. But for now, I just wanted to get the windows working.  I had stupidly left them down when I took the switch out (!) and I just wanted to get them operating.

As a temporary fix (mainly to get the windows back up), I made a little jumper from a resistor lead (you could use whatever you have handy) and connected terminal 11 to terminal 10.  You can see it in the picture.

And voila! I had voltage to the front windows and they rolled up!


All that for a sticky switch, which does seem to be a little better now.


Post a Comment 5 comments:

  • Unknown said...
    January 16, 2017 at 6:51 AM
    Thanks for posting this it's been very helpful!
  • March 5, 2017 at 11:13 AM
    Great write-up, pictures help alot! Thanks!
  • Rick G said...
    July 20, 2017 at 7:08 PM
    I just had the exact same problem! I will be trying your jumper solution. Have you traced and rewired the lead to terminal 11? How did that go? Thanks!
  • Yr Fthfl Blggr said...
    July 22, 2017 at 9:13 AM
    If you look at the schematic, the hot side of the circuits for the front and back windows originate at the same place. They do go through separate fuses after that, then on to the window motors and switches.

    But after I saw that, I didn't bother tracing the front window wiring back to find a break. I suppose you could, but it goes through the harness under the center console, and I'll be honest, it was too much of a hassle to take on. The car has been fine with the jumper in place.

    As long as you have voltage on terminal 10 or 11, the jumper to the other one that is dead works fine.
  • Unknown said...
    July 22, 2017 at 1:46 PM
    Great. I was worried about the potential for a fire. Thanks!

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