Brake warning light, The quest for success continues Options

[technicalninja]

Pulling the flasher unit might be another "eliminate stuff test".

When I'm hunting an electrical gremlin "divide and concur" is one of my processes.

[PaIsa]

(IMG:style_emoticons/default/av-943.gif) (IMG:style_emoticons/default/headbang.gif)

Oh man, that is a crazy set of symptoms.

I’m going to have to do some thinking on that one.

Looking at how that harness is taped up, someone has defiantly mucked with it.

What build month is your car on the door post label?

Happy to help you step by step when the time comes. (IMG:style_emoticons/default/beerchug.gif)

Thanks again for the support. Cannot answer on the build month as the sticker is no longer there. The car has been resprayed at least 2 times!!

Karman plate no longer there as well!

[PaIsa]

@Literati914

So was your harness brown/yellow all the way up to the back of the gauge and also down at the master cylinder switch?

I thought that was the case.. but I just checked. The wire going to my Ebrake handle is BR/YL (like the original poster verified his was originally)..while the wires going to my brake warning switch @ m/c is BR/WH (besides the BR ground wire).

Just a mistake on this particular diagram? I don't know, probably (IMG:style_emoticons/default/confused24.gif) . My harness is original, build date 05/72 I believe.

@PaIsa - I asked earlier, why the seat belt warning lines are disconnected... I understand it's popular because of the annoying buzzer but from memory I think it needs a particular "loop" of wire to bridge two points on it's relay (that's under the passenger's seat). I'm suggesting that if it's not correctly done it may cause a flashing light warning for the situation. Have you looked at the wiring under the passenger seat? I'm just guessing here.. but I'd check if you haven't already.

I removed both seat twice in the last 2 days and there are no wires under the passenger seat. I looked through the opening with the ash tray removed and I cannot feel any wires that would be used for this seat belt warning system. The dash seems to have the cutout for this, but it is not there.

[Dave_Darling]

Have you checked the electrical switch in the side of the brake master cylinder? If you mentioned that, I missed it.

There's a switch in there that gets tripped if you lose brake pressure in the front or the rear brake circuit. (Say, if you boil your brakes, or have a brake line failure. Or if you just bleed the brakes.) It should have a reset button covered by a rubber nipple. Press the button to reset the switch.

Some switches do not have the reset button (they may be from a different model of car?) but those should reset by themselves when the pressure imbalance goes away.

A brown and a brown/white wire should go to the switch. The switch will short those together when it detects an imbalance. (Or rather, when a piston between the circuits gets moved by them having a large pressure imbalance.) Some switches only have a single wire connector; those ground through their threads. So the brown/white wire would be hooked up to them, and the brown wire taped up somewhere out of the way.

This switch, or the wiring to it, could also be the source of the brake warning light being on.

--DD

[Literati914]

Have you checked the electrical switch in the side of the brake master cylinder? .. It should have a reset button covered by a rubber nipple. Press the button to reset the switch. ..
--DD

Dang, so of course we forgot the switch on the m/c !! The obvious stuff first and (IMG:style_emoticons/default/agree.gif) with Dave, good call.

[PaIsa]

Have you checked the electrical switch in the side of the brake master cylinder? If you mentioned that, I missed it.

There's a switch in there that gets tripped if you lose brake pressure in the front or the rear brake circuit. (Say, if you boil your brakes, or have a brake line failure. Or if you just bleed the brakes.) It should have a reset button covered by a rubber nipple. Press the button to reset the switch.

Some switches do not have the reset button (they may be from a different model of car?) but those should reset by themselves when the pressure imbalance goes away.

A brown and a brown/white wire should go to the switch. The switch will short those together when it detects an imbalance. (Or rather, when a piston between the circuits gets moved by them having a large pressure imbalance.) Some switches only have a single wire connector; those ground through their threads. So the brown/white wire would be hooked up to them, and the brown wire taped up somewhere out of the way.

This switch, or the wiring to it, could also be the source of the brake warning light being on.

--DD

Yes I know of that switch. I have the 2 poles switch and it does not have a reset. I did some test with this switch disconnected and making sure that the 2 wires going to it were not grounding and still the brake warning light was flashing so my understanding is that this is not this switch that is the cause for the brake light flashing.

As I said, I will put this troubleshooting to rest for now and look at it deeper during the winter in a more detailed approach looking at each wires and understanding were they are going and better understand the circuit.

[PaIsa]

One last comment/question before I put this to bed before resuming work on this during the cold season.

Why would Porsche/VW would put the wire for the E-brake switch outside of the pretty well taped main wiring harness that runs from front to back (or back to front). In one of the photo I have put in the thread, we see what I believe to be the original wire for the E-brake running aside the main wiring harness. Why would someone run a single wire through the tunnel when it could have been taped and fish through with the main wire harness??

I have looked at parts diagram and it seems that this wire should effectively come from the main wiring harness.

Some more searching to do the next time I take out the seats and center console!

[Superhawk996]

Your harness tape is not original nor is the way the wire is routed.

DAPO has been in there mucking around and very likely is the source of your very odd symptoms where the state of the warning light and the functionality of the parking brake switch seems to be dependent on whether or not the engine is running. Very unusual.

Out of curiosity, do all your turn signals function properly regardless of engine on/off?

[PaIsa]

Your harness tape is not original nor is the way the wire is routed.

DAPO has been in there mucking around and very likely is the source of your very odd symptoms where the state of the warning light and the functionality of the parking brake switch seems to be dependent on whether or not the engine is running. Very unusual.

Out of curiosity, do all your turn signals function properly regardless of engine on/off?

Status of turn signal operation:

No key in ignition: not working when selecting either left or right (I guess this is normal)
Ignition ON: turn lights work without a problem
Engine running: turn signal work without problem

I guess you are right about the wiring harness as I what seems to be the way in was done at the factory was with a kind of fabric tape and it was taped so that you were able to see the wire (not fully taped with shinny electrical tape like in my case!)

[Dave_Darling]

With no key in the ignition, the "parking light" feature of the turn signals should come on when the turn signal lever is up or down.

Someone has been mucking with the wiring.... That makes it even harder to figure out WTF is going on.

--DD

[PaIsa]

With no key in the ignition, the "parking light" feature of the turn signals should come on when the turn signal lever is up or down.

Someone has been mucking with the wiring.... That makes it even harder to figure out WTF is going on.

--DD

Just verified this again and yes the turn signal actually come on without the key in ignition on the turn signal lever up or down. So this part seems to work as expected.

[worn]

Thanks for the good reply.

I have a DMM and I know how to use it for basic measurement (voltage, resistance, continuity, etc.)

I have the generic wiring diagram for year 72, but there seems to have difference with my car since there are things on the wiring diagram that I don't have like the ''Seat belt warning'' under the ash tray. I will look at it a bit more and try to go deeper with my diagnostic effort.

For the colors of the wire going to the E-brake switch, I will dismantle the internal of the car again likely today and take a picture of the wire to confirm the colors. Is it white that seems to have turned yellow, who knows!

Now this morning I tried something since when I go the ignition ON, the brake warning light was flashing and I was earing a clicking. I got the key out of the ignition and pulled the hazard light and while the flashers were working, the brake warning light was also blinking and I was earing the same clicking which is likely the turn signal (flashers) switch. Reading Dr914 tech tips, tip #723 states: ...This loss of pressure can also be indicated with a constant clicking of the turn signal switch at your left knee under the dash... Any link here? The solution to this problem appears to be bleeding of the brakes. I will do a test today with the MC switch disconnected.

I will keep you all informed.

Thanks

Interesting. My ‘72 also came with the wires you have, but without the wires ever being used. They were taped down near where the wires for intermittent wiper relay were. During the restoration I bought the proper reservoir and cap needed to produce a low fluid warning. Never saw the wires on a diagram, and no one else seemed to know anything about it. Wish this would show up in originality, or that I had found the thread if it is indeed there.