Andy P

Sorry to ask about this commonly asked problem. I have searched through the archives, and this has given me some useful info, which I have checked out. Thanks also to Elliot Davies for your advice. Unfortunately I have still failed to solve the problem.

Car is a German supplied ’92 LHD RS Lightweight, with chassis No.: WPOZZZ96ZNS491620. I have had the car on the road on and off for a week or two.

Here are my observations/investigations (in no particular order) to date:-

1) Spoiler does not raise at all automatically now, but did raise at around 100km/h but dropped at around 60 - 70km/h, or just randomly at or around these speeds. I have noticed on a couple of occasions though that the spoiler would raise at about 140km/h, then drop a few seconds later.

2) Warning light does not go off until 120km/h, this now seems to be a consistent occurrence.

3) Manual control on centre console works just fine, always has done, though when raising the spoiler the relay behind the switch sounds to be clicking twice - normal?

4) Have checked the micro-switches on engine lid and they function correctly, i.e. with someone operating the manual control, closing either of the micro-switches stops the spoiler. Have also checked the switches for continuity and resistance and they check out OK.

5) Have stripped the centre console manual switch down, and all the internals look clean and correct. Have also checked the switch for continuity and resistance and it checks out OK.

6) Main control unit - is this the silver aluminium VDO box (measures approx 120mm x 90mm x 40mm) under the dash’ behind the ignition switch? If so, it has the following info on the decal:-
”VDO”
”964.641.330.00” (part number obviously)
”410.209/013/001”
”V4.7.6” “3.92” (build date)

7) If manually raised, the spoiler does not go back down when vehicle stops.

8) Engine lid earth strap OK with clean contact surfaces.

9) Spoiler mechanism well greased and runs smoothly.

A friend has a similar age and spec RS, which I plan to swap control units between. After this I am out of ideas!

Any other ideas?

Many thanks.

Andy P.

Gary C2

Andy,
Given your information, the problem is either the spoiler control unit or the speed input to the spoiler control unit. Swapping the boxes is the simplist check to determine which it is. If it's the speed input, first check that wire for a short or open circuit. If you have access to a scope, that would help a lot to troubleshoot the source.

Gary

Andy P

Thanks Gary. Is the control box I describe in note 6) the control unit for the spoiler?

I do have access to a scope, do you know which wire(s) or pin position is the speed signal and what type/magnitude of signal I should expect to see?

Thanks.

Andy P.

Gary C2

Andy,
I believe the part number should be 964.618.212.00. The speed input to the control unit is pin #12. The signal should be a squarewave with an amplitude of either 5 or 12 volts.

Gary