Gregor1

Dear Fellow Fanatics

After not having driven my 91, 964 for 5 weeks ther rear spoiler operation is erratic. Can anyone help?

I receive the standard malfunction dash-warning light past 46 mph because either the spoiler has not deployed at all or sometimes it is stuck in the halfway position...either on its way up or down. Even when I try to override the automatic operation via the manual selector switch it seems to only react 10% of the time and also gets stuck in the half way position.

I checked for blockage or loose wires but could not find anything. When I pull the fuse and reset it, it usually works the first time and then again intermittent. Does anyone out there have any idea what my next move should be. Is there a test I can perform or is there a single component that is usually the first to diagnose ?

Thanks
Gregor

Adrian

Dear Gregor,
This problem appears to be mechanical in nature. You need to look at the motor, the drive cable the transmission or the spoiler mechanism itself. It may just need lubrication. You use a light graphite grease. I strongly recommend you stop and fix this problem before you end up causing yourself some expensive repairs. This I am afraid is a get your hands dirty job. You might want to get somebody to operate the spoiler for you whilst you are at the rear with the engine lid open watching what is going on. You do not need the motor running either to do this. Just watch the battery.
Ciao,
Adrian
964C4

johnfm

Gregor

I have had the same problems recently - generally erratic spoiler behaviour. Not going up - or staying up when stopped. Not responding to the manual controller - sometimes. Eventually, it just stopped working altogether a couple of weeks ago.

I 'think' its a problem with the electronics that control the spoiler, the little grey box inside the car. I think this can get a bit confused, maybe by conflicting inputs from speed sensors and microswitches. I draw this conclusion as, after checking my spoiler systems (microswitches, motor etc) for operation, I found them all working. So, I used an outside power source to operate the spoiler up and down. I suspect this may have somehow sorted out the controller, as I have no problems at all for 3 weeks now.

The controller is always powered, that is, there is 12V going to it without ignition, so maybe a battery disconnect will help.

Good luck

Adrian

Dear John,
Gregor says his spoiler is stuck halfway. This is normally a mechanical jam and the control unit has a 15 seconds current draw detect cct for this.
I suspect when you applied 12V direct to your motor that cleaned off the brushes and commutator. This is an old aircraft electric motor trick we do. Bypass the transistor drive cct and apply straight 28V. Spins the motor up and cleans out the crud (carbon) from under the brushes.
Ciao,
Adrian
964C4

johnfm

Adrian

have you noticed that the spoiler controller is always live? And why is it hard wired, rather than a plug fitting? I'm surprised this isn't a possible battery drain culprit!!

Gregor1

Adrian and John F.

Thank you both for your advice.
Nice looking car Adrian. By the way my brother is a pilot on a G4 in Switzerland (Sennwald)
Anyhow I will try the graphite grease trick today, it very well might (I hope ) do the job. On the other hand....you should know that I disconnected the battery for 5 weeks and then connected it when I came back. So maybe it was a "hard" reset the system did not appreciate ?
I'll go step by step.
Thanks again
Gregor

aalonzo

Does anyone know where one might obtain parts for a rear spoiler for an 89 C4. One of the nuts fell out of the spoiler mechanism, the lower right nut at the joint that balances the right side of the spoiler as it goes up. Thanks

Adrian

Dear John,
This is a Porsche thing that I happen to disagree with. Many components are hard wired with 12V but are not activated until they receive an earth. YES all these components (control units) are potential current drains. It was more complicated to use ignition on distribution switching logic so Porsche did the earth seeking method.
I have not known a rear spoiler control unit cause a current drain because there are current draw switch off devices within the control unit so these would have to fail first. These kind of failures are not considered in fault analysis unless it is safety related and this is not.
Ciao,
Adrian
964C4

PS: Aalonzo. You could try the wreckers first and if this fails I am afraid it is off to your local Porsche parts supplier.