simonstorey

Hi,
I just reinstalled the stock deck lid on my 1991 964 yesterday.
Also had to reconnect the control unit (behind glove compartment) and also
pop in a 15A fuse in the fuse box.

Manually the spoiler works & also rises at speed although it does not retract when slowing back down.

I've checked the micro switches in the tail for function and they are good. The control unit in the cabin also clicks when the spoiler hits the max and min travel so I know the signal is at least getting to the control box from the micro switches.

I'm also getting a spoiler warning light on the dash at startup although it goes off as soon as the car is over 5mph or so...

It seems like everything works except the signal that the car is slowing down isn't getting through.

Maybe the fault just needs to be cleared for the system to function properly?
Anyone been in a similar pickle?

Thanks!!

A8KED

I can't help with the spoiler not going down. According to the owners manual the spoiler light on the dash is suppose to stay on until you are going over 5mph. Mine does this too.

simonstorey

Oh, wonder why it does that?
Well at least that part of the operation is normal!! It makes it even more mysterious then why the retract is not working.

mojorizing

It sounds like the module could have a bad component on the retract circuit. The module extends/retracts from one speed input going into a MC14538 monostable multivibrator. Two different RC circuits effect point where the spoiler extends/retracts. You need to remove the module and closely inspect the components for a cold solder joint/ broken trace, especially the components on any trace connected from pin 14 of the MC14538.

MC14538 is the chip on the upper left hand side, components to look at are the two yellow capacitors in the middle left hand side, the two red resistor networks on the lower left hand side and the group of 6 diodes middle lower. Both sides of the module could have a bad solder joint.

https://rennlist.com/forums/964-foru...ml#post9333880

simonstorey

Awesome. Thanks for the tip.
Time to dust off the soldering iron!

tfitch03

+1 I would check the solder joints. I bet that fixes your glitch.

simonstorey

Will do. Start with the easy stuff...then move onto replacing stuff.

Earlydays

When my spoiler worked when using the switch and would raise, but not retract automatically it was the "control module".

simonstorey

Yup that seems to be the issue.
I'm replacing the transistors inside the module later today. I'll update after a test drive tonight!

Also if anyone needs any transistors let me know. I ordered 100 and only need about 6.

mtnbikeman123

How did the test drive go? I have these same symptoms so I will likely have to perform the same fix.

simonstorey

I've replaced the transistors, the capacitors and one diode that looked funky.
So far no luck!

This morning I sent the unit to

Systems Consulting
3520 Maple Ave
Manhattan Beach, CA 90266

Should be able to repair for $135.

email Loren at lorenfb@verizon.net

Maybe the repair would work for you as it seems to for others.
With mine it looks like it's a component that I can diagnose that's not working.

r-mm

Found your old thread when I was greeted by an deployed spoiler in the parking lot today. Like you I have no fault signs or maladies except lack of retraction. Can we presume the control unit repair solved this?

simonstorey

Yes and no.
The repair worked - for a while.

Ended up with a used unit from ebay that came off a Singer build.
There's an ebay seller that gets all the Singer parts.

r-mm

But one way or another the non retract problem lived in the control unit?

simonstorey

Yes that was my issue.
I believe others have found fault in the contact switches for the spoiler.
They are easy to find and test.