924Board.org

[chipschwarze]

My 79 924 has a strange problem when. When I hit the brake pedal, both the light on the dash and the light on console under the fasten seat belt lights come on. When I set my parking brake, only the one on the dash comes on. When I turn sharply back and forth making the car sway, both lights will come on. I have checked the fluid levels, they are fine. Brakes work good, no mushy feel. Any ideas on where to go with this problem would be appreciated.
_________________
79 924 project car

[Smoothie]

First check the MC switches - both of them have to be good + with good connections for your brake warnings to work correctly. Second possibility is that there actually is something wrong with the brakes, but since they seem to be performing well, check the switches first.
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[chipschwarze]

Thanks for the input. How do these switches work, and what should I look for when checking them? Are they pressure sensitive, ie looking for drops in break fluid pressure?
_________________
79 924 project car

[Smoothie]

Look at your Haynes manual, pg 260 - that's the 3rd page of the wiring diagrams for your car. At left are the switches, rear brake lights, and warning light. From the horizontal line about 1.5" from top you can see where power is supplied by the re/wt wires running from "C19" to the "82a" posts at the switches. (Yes, the "P" in the box on each switch indicates they're pressure switches.) When all is well, both switches move to close the contacts between 82a-81, and power is sent only to the rear brake lights. -But if only one switch closes, power runs from 82a-81 and on to the rear brake lights, and it also loops around to pass through 81-81a at the switch that didn't move, and from there it flows down to the brake warning light to light it also.

You can also see from the diagram that if both switches don't move, you get nothing, no power to the rear brake lights and no power to the brake warning light/s.
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[chipschwarze]

Thanks for taking your time to help me with this. I am finding that I like this car, it is kinda fun.
_________________
79 924 project car

[Smoothie]

For more fun, trace the brake warning circuitry further and you'll see that the oil pressure light switch is also tied to the brake warning light. -So the brake warning should also light whenever your oil pressure light comes on. In fact, this could be why you get the brake warning when you turn quickly side-to-side - it might actually be a brief loss of oil pressure on each turn caused by the oil sloshing away from the oil pickup. To verify, look for the oil light flashing on along with the brake light. -And if that's the cause, obviously stop doing it.

Actually, the brake warning light appearing on hard braking could be caused by the same thing (oil sloshing away from the pickup). Again look for the oil light appearing at the same time..
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[chipschwarze]

How did you get to be such a wise old dog. You must have owned your car a long time. Thanks for your expertise, it is greatly appreciated. Your last post made me go check my oil, I had it in to Jiffy Lube yestarday. There is oil running all down the filter. somebody did not tighten it. Guess I should not get in a hurry and do it myself from now on.
_________________
79 924 project car

[Mike924]

Smoothie strips his car down completely every Friday night, takes some pix of the bits on Saturday, then puts it all back together on Sunday ready for Monday morning!
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[Nobbi]

I guess smoothie owns a " Monday-Morning" car which had so many defects that he becomes a perfect mechanic.
My self, i own my 924 since 20 years and i own it so long because there wasnt nearly anything to fix in that time.
Ok, my car isnt good for a contest,but, driving it on a nice day is still making me scream.......

Nobbi

[Smoothie]

No, you have me confused with someone else, and nobody takes their car apart and reassembles it every weekend anymore. Lizard used to do that though.
Actually, mine's been pretty reliable, and the most reliable used car I've had (and I've only had used cars). That first year auto shop class I took while a senior in HS has paid off well. After that I was stationed at a shore base in the Navy that had an on-base auto shop - that and owning a Fiat as a first car (that needed fixing constantly) rounded out my auto repair training. Got my 931 in '92, so that's 15 years, and have probably learned more about it by looking up, and reading about problems others have had here. That little oddity about the brake warning light turning on when the oil pressure's low, I found within the past year while perusing the schematics to answer someone elses' question. I don't even have the MC with the pressure switches, but a fluid level switch in the brake fluid reservoir cap instead. The rest of it works the same though, lighting both the oil and brake warnings when oil pressure's low.

Yes, stay away from Jiffy Lube and the others. Even if they do everything right, you still end up with cheap oil and cheap filters. -And as part of their free additional service, they might just top off your power steering fluid with windshield washer fluid, and do other idiotic stuff that you won't know about until things come to a grinding halt.
Don't even drive by these places - your car will develop a nervous tic.
-And if you have the same luck that I've had with mechanics, you'll want to do all mechanical work yourself too.
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[Mike924]