Bales

Thank-you - here it is on my workbench.

Next, how do I test the transistors? And is there anything else I should test?

Schocki

I just replaced them. Very cheap and most of the time the problem.
Clean the electrical contact surfaces with a white eraser WYAIT.

Bales

Have contact cleaned the surfaces. Noticed that the original resistors are are BC337-25 and BC227-25. The replacement ones I can find locally are BC337-LZ and BC227-LZ. Can't seem to get any sensible info via google on the differences except that 25 means the current gain. Does it matter?

StratfordShark

The suffix doesn’t matter.

Your googling will have revealed the pin outs for the transistors.

To test them, use diode test position on your multimeter or the low resistance range. You should have diode working (near infinite resistance one direction, low resistance the other) between base and collector, and base and emitter. Very high resistance between collector and emitter.

Note the transistor should be out of circuit for these tests so desolder each or snip the collector and emitter leads and resolder if good.

This vintage board is wonderfully easy to work on, like all 928 electronics. The other day I went through surface mount hell removing tiny wiper relay from a control board on my son’s VAG group car. This after having to remove seat to attack the 11 firmly attached multi-way plugs connecting the board - located in the most awkward position above pedals - to the various switch and signal looms.

Bales

Thanks Stratford.

Four new transistors soldered in. Pretty easy, quite pleased with the tidiness of the work considering the last time I can remember using my soldering iron was 1999 (yes it's that old!). Turns out my multimeter has a neat little panel for testing transistors, none of the ones coming off the board worked.

Plugged the motor back into the car harness, turned on ignition, moved HVAC slider and..... the lever arm moves through the full range :-)

Reconnected the arm that moves the mixer flap, and on rectangle vent setting am now getting a closed water heater valve - looking good!

Still need to fully test, and take the car out to get warm and see if it all behaves.

StratfordShark

That’s excellent news on fixing the setting motor!

Schocki

Good to hear that my tip worked. Same happened to me and others in Europe too.
You'll see that everything is good with the HVAC now.
Let us know how your test drive goes.

Bales

Was super pleased until... a package arrived from Garage9 with goodies for the car, so was installing interior LED bulbs and dropped an old bulb down the side of the drivers seat. Moved the seat all the way forward so fish it out and now the seat is stuck in the far forward position! Press the switch and nothing. Power is good elsewhere so not a fuse (checked them also). Tried giving it a bump or two, no joy. Went to use the manual adjuster and found the cogs have broken teeth... Looks like either the switch has gone or the mechanism is jammed. So have given up for tonight, that is tomorrow's problem to solve. Once solved I will test drive and report back. 1 step forward, 2 steps sideways...

G.P.

If you decide to pull the seat switch apart and clean the contacts, be careful, the springs and ball bearings like to blast out and explore various parts of your garage. I suggest doing the final disassembly with the switch in a plastic bag.

Cheers,
Gary
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Bales

Attached a spare battery to the seat motor and she whirred back into place. Must be a switch issue, something for next weekend.

Took the old girl for a long drive today, everything worked as it should :-)

Cool air, but not cold, so looks like next step is to re-gas the AC system.

Thank-you so much for your assistance. I have no idea how you'd own one of these cars without the help of a community like this :-)

Schocki

Sounds good and an easy fix after all.

If your AC is equipped with a sight glass at the receiver drier, use it to slowly fill up the system.
Is you see foam or many bubbles, the system is slightly low on refrigerant.
Add only so much until the foam/bubbles disappear. This should take care of it.