Brake warning light, The quest for success continues Options

[PaIsa]

So I am back trying to get my brake warning light to work properly. The situation before I started searching for the solution was the following:

Brake warning light was always blinking whatever the car condition. Blinked with the ignition ON. Blinked with the engine running and hand brake applied (normal). Blinked with the engine running and hand brake removed. Blinked with the engine running, hand brake removed and MC wire disconnected. So basically, blinking all the time!

So I was investigating the emergency (hand) brake wiring. Remove the seats, center console, etc. Looked at the emergency brake switch and seemed to work OK. There was a contact (closed circuit) when the switch was in position where the emergency brake would be applied and no contact (open circuit) when the hand brake would be removed. Looked on the wiring for evidence of short to ground but was not able to find anything. The wire goes in the center tunnel and is accesible until the shifter where rather then following the main wiring harness and the speedo cable, it goes under and God knows where it goes!! So I was not able to follow it all the way.

Now I have some disconnected wires near the brake fluid reservoir (already a thread on this trying to understand where these should go). The wires are brown-white and brown-white connected with a brown wire. The brown-white wire that is connected with the brown wire is cut.

So after I reassemble the emergency brake wiring, I did some test again.

Ignition ON, the brake light comes ON. Whit the engine running, no more brake light blinking.

So now I tried with the cut wire (the one near the brake fluid reservoir) reconnected. Brake light blinking all the time. Disconnect the wires, no more blinking when the engine is running.

I am lost. Even writing this I am not sure if I am right with the tests I did and the results I got.

Anyone has any advice? I looked at the wiring diagram, but not sure!!

I would like to have this working but don't want to go crazy with this!!

The car is a 1972.

[PaIsa]

Thanks for all the answer. I knew my initial message was not really clear, but here are some more details:

Wire going to the E-brake switch: The wire has been hacked through the years. A new cable was tied in to what seem to be the original cable in the tunnel somewhere between the 2 seats. The original wire seems to be brown-yellow, although I would have thought it would be brown-white. In the image blow, we see the wire going to the E-brake switch (yellow wire running behind were should be the driver seat. The tie-in to the original wire is where there is white electrical tape. We can see on this image that the car has the wiring for the seat belts, but they are not used. As for the switch, I cleaned the switch and where it makes contact to the body for the ground before reinstalling it. Now for the stupid question: When testing this cable/switch with a test light or voltmeter, I guess that with the switch in E-brake engaged position, I should measure battery voltage or the test light should come on (with ignition ON). Is that the case. If not then it means that it is grounding or disconnected elsewhere. But since the original wire is going literally in the tunnel, it will be difficult to track it down.



Hope this is a bit clearer and that it will bring some more good comments in trying to get this resolved.

Again many thanks.


Now for the wires near the brake fluid reservoir. I found those wires last week. Before I did not knew thay existed and the brake warning lights was always blinking. The wires were find in the way shown in the picture with one of the wire cut. Probably that before I found those, the cut wire was grounded making my brake warning light blinking. Now if I have the cut wires not grounded or connected, then my brake warnig light does not blink with the engine running (but it does light up with ignition ON). So I guess that the wires are part of this circuit, but was not able to find them or understand where they were on the wiring diagram.

[Superhawk996]

Now for the stupid question: When testing this cable/switch with a test light or voltmeter, I guess that with the switch in E-brake engaged position, I should measure battery voltage or the test light should come on (with ignition ON). Is that the case. If not then it means that it is grounding or disconnected elsewhere. But since the original wire is going literally in the tunnel, it will be difficult to track it down.

To answer your basic test question. When the brake switch is activated - brake lever up, the switch completes the circuit to ground, that is all. That ground is easily verified up at the back of the gauge. If it isn’t showing up there, you have wiring problems between the switch and the gauge.

Please don’t take this the wrong way, my intent is to be helpful.

Forget about it for the moment.

Spend the time to understand the wiring diagrams (especially Spoke’s) that had been provided already. Get a digital multi meter (DMM) if you don’t already have one. Simple test lamps are not going to be very helpful to what you’re trying accomplish. Spend the time to learn how to use the DMM on simple circuits on the bench if you haven’t used one previously. YouTube is a great source for learning the basics of DMM use and electrical troubleshooting.

Understand that your car has wiring that has been previously hacked up. This always makes things more challenging.

Your car potentially has some wiring that is non-standard for 72’ and/or poorly documented - talking about this supposed brake fluid sensor wiring. Likewise if you have brown / yellow wiring instead of brown / white that is odd. Are you sure the yellow stripe isn’t just an aged / yellowing of what used to be a white stripe? (IMG:style_emoticons/default/confused24.gif)

The brake warning lamp flasher circuit and associated flasher relay isn’t the most intuitive. Ask questions if needed to understand exactly how that circuit works. Here is a link. See post #5.
http://www.914world.com/bbs2/index.php?showtopic=53850

You can do this but it is worth spending the time to learn to troubleshoot electrical issues on something easy on the bench vs trying to do it on the fly on a problem like you’re experiencing. It is almost impossible to troubleshoot effectively if you can’t predict how the circuit is supposed to work and what you should be measuring / testing.

[PaIsa]

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