jim morehouse

I had a burned out taillight and the resultant warning and replaced the bulb in my '88 S4 (164K miles). Now I have a "stop light" warning. Had someone stand behind the car and the brake lights are working. Remembering a post about changing both sides to get equal resistance I did that (after about 80 miles of driving w only one new bulb and one old). No help.

This is the part that puzzles me:

The warning light comes on as it should when I start the car and stays on after I depress the brake pedal. If I push the pedal down just an inch or so very slowly, the warning goes off. Push it further and the warning comes back on.

I'm going to do the 'clean contacts/grounds' but thought the pedal behaviour was strange and might point to another area. Any ideas?

thanks,
Jim

heinrich

First thing I'd try now Jim, is a swap of the lamp control module.

AO

H-
You overreact sometimes...

Jim-
Clean the contacts. Maybe try another set of 2 new bulbs. It's a lot cheaper and easier IMHO.

Shane

Agreed^

I had the same thing happen to my '86.5. Changed all the bulbs, cleaned contacts and grounds, kept getting the stop lamp warning. Swapped the lamp control unit (bolted to the pass. map tray) and all was fine again.

touque

Jim - have you looked at the factory work-shop manuals? There's a guy on Rennlist here that you can buy them from ...

j/k. I have the same issue actually and have tried everything but the swap of the lamp control module... guess that's next

Troy

MarkRobinson

ENsure you have the correct wattage bulb in there: I had a wrong wattage in one of mine once, it triggered that warning. Most Sylvania auto bulbs are NOT marked "European" as they require for the Porsches.

AO

Based on Shane and Troy's comments, I'd like to retract my previous statement about H overreacting. Whodathunk... ?

SharkSkin

Your car has a separate warning for low fluid/ system imbalance, right? I don't recall whether your car has the two switches on the master cylinder, but if it does you may have a fault in one or both of those.

Shane

Well to your defence, I seriously doubt I would have just up and bought another control unit, without trying every other trick in the book first. Hell I might not of replaced it at all for that matter since my light were working just fine. Just that the warning light was getting annoying.

Fortunately (gotta see the good in all things) I had a very crispy (Extra krispy when compared to chicken) 86 auto sitting there with a perfectly good lamp unit doing nothing. Ten minute swap and all was good.

fabric

I nominate this as post of the day.

WallyP

Jim,

Don't forget that the CHMSL will also trigger the stop lamp warning...

dr bob

Jim--

Which car are you working on? (Darn-- participle just flapping right in front of a question mark. Again! The grammar police or the ghost of Gene O'Rourke will surely get me now.) On which car are you working, Jim?

The early car has two switches on the master cylinder. If either one fails, you'll get the phenomena you are describing. It will also happen if one hydraulic circuit of the brakes is failing. Those hydraulic circuits never fail though, that's why they put in multiple switches.

touque

thanks Chris... I've waited a long time to use that line! hehe

jim morehouse

Man, you guys are tough. Ok, I didn't look at the manuals...not sure it would help though. Wally, is the "CHMSL" the center high mounted stop light? Haven't seen that abbreviaton before. I used 1157K bulbs to replace the bulbs and I think that's the correct one. I'll post on further results...that alarm light is really annoying and I can't keep it off since it comes on whenever I press the brakes. I'll have to check w Capn Earl to see if he has a bulb check unit I can try swapping.

thanks,
Jim