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Sun Aug 17, 2014 1:35 pm

I have a 1983 Vanagon 2.0L air cooled automatic. I recently replaced the brake master cylinder and both 3 pronged switches that attach to it with new parts. I've bled the brakes and topped off the brake fluid. The brakes function well but now my brake warning dummy light, on the upper left side of the instrument panel, stays on constantly. It goes off only when I step on the brakes! This happens any time the key is on, whether the engine is running or not.

My understanding is that only two things will turn on that light. Pulling on the emergency brake handle or low brake fluid. I removed the hand brake boot and checked the switch. Appears ok. I unplugged it but the light remains on.

I don't see any type of sensor that checks the fluid level of the master cylinder. Is there such a thing on this year? If I unplug either one of the two brake light switches, attached to the master cylinder, the brake warning light remains on. It only goes out if I have both switches unplugged at the same time. I've tried reversing the connectors to the switches but it made no difference.

Any ideas? I'm at a loss.

Sat Aug 23, 2014 2:19 pm

Here's what I found. 1984 air cooled Vanagons don't have a brake fluid level sensor in the cap. The 3-prong switches are the only indicators of a failed master cylinder or a problem with the brake light circuit. The only other reason the dummy light should go on is if the hand brake is on or hand brake switch has failed (stuck in the on position).

I had installed a new brake master cylinder. Later I ordered the two brake switches (3 prong - correct for my harness) seperate from the master cylinder. After installing the switches I discovered the problem with the brake warning light (dummy light) staying on unless I applied the brakes, which would turn it off only while the brakes were applied. After extensive testing of the the wiring, the switches, the connector at the dummy light and the dummy light circuit board I could find nothing wrong.

I decided to test the resistance between the terminals of the new switches as compared to one of my old switches that I still happened to have.

If you look very closely on the harness connectors you can read the terminal numbers on the white plastic.. Looking at the unplugged harness connector, facing you, the horizonatal pin is 8a, the left vertical pin is 81 and the right vertical pin is 82a. On a 3-prong switch, terminal 82a is connected to terminal 15 (power always on). Terminal 81 goes to the brake lights and completes the circuit with 82a when the break pedal is applied.

81a is the lead that goes to the dummy light on the dash. 81a should not receive power unless one of the switches fails to switch, then the other switch acts as a back-up, routing power to the brake lights, so that they still function, and also routing power back through the failed switch, from 81 to 81a, and on to the dummy light to indicate a problem with the switch.

There should be infinite resistance between terminals 82a and 81a (no connection) and also between 82a and 81 (default: un-switched) with near zero resistance between 81a and 81 (internally connected by switch).

Instead I measured infinite ohms between 81a and 81 and also between 82a and 81. I measured zero ohms between 82a and 81a. The new switch terminals 82a and terminals 81 were reversed on both switches! This gave power from 82a to 81a continuously. 81a is the lead to the dummy light. Hence the light staying on continuosly.

I pulled apart the switch connectors from the harness and reversed the two wires 82a and 81, re-connected the harness to the switches and then... eeehah, everything worked correctly!

I don't know if I was sent the wrong year/model switches or if the switches were just manufactured incorrectly but buyer beware.. if you experience the same problem this may be the reason why. Simple fix but difficult to track down!

I found a great post, with a 3-prong switch wiring diagram, that really helped a lot in figuring this out. You'll find it about two thirds of the way down the page:

http://www.thesamba.com/vw/forum/viewtopic.php?t=529137&highlight=brake+light+switch+test

Hope this helps

Sat Aug 23, 2014 2:31 pm

Thanks - that answers some questions I have had awhile.

My warning light came on recently -- I suspect it is telling me one of the 2 switches has failed. Its about time for that as they seem to last about 2-3 years.

Sat Aug 23, 2014 10:35 pm

I haven't tried it yet but here is a procedure you can try, for a 3-prong switch, to determine which of the two switches is bad.

You can get to the switches by first removing the instrument cluster. You can remove the brake warning light from the instrument cluster, so that you can move the instrument cluster out of the way, but leave the harness connector attached to the brake warning light assembly. Loosen the connectors from the brake switches enough so that they are still connected but so that you have enough room to make contact to the spades on the switches with a voltage test probe. It will be awkward but you should be able to get to it.

Turn your key to the on position. Apply the brakes. If I'm not mistaken, there should be voltage between terminal 81 and 81a on the switch that is bad. The switch that is good should show voltage between 81 and 82a and there should be no voltage between 81 and 81a.

Sun Aug 24, 2014 2:32 am

I recently experienced the same issue that Cybervette wrote about above. I gleaned the wiring schematics to learn the function of the two switches.

So, I determined that the switch closest to me, looking at the master cylinder from behind the steering wheel, had gone bad. I unplugged it. Brake lights still work and park brake light doesn't come on unless the handle is engaged.

I do plan to replace the bad switch, as Cybervette indicated, having two switches provides for a back-up if one of them fails.

Sun Sep 21, 2014 11:07 am

(1980 Westy)
I have sort of a reverse issue. My light doesn't stay on. It will intermittently flicker at a certain reach while using the foot brake. I have never had an issue before, it just started on my last trip.

So while driving, applying brake at high speed, it sometimes flickers on. If I maintain the position of the brake pedal when I see it come on, it may stay on a few seconds. It does not come on consistently every time I use the brake. Always at random an only a quick flicker. It functions properly with the hand brake and turns off when I release the park brake.

I am getting a sense that there's a fluid level sensor in this system from some previous comments? Ill check my fluid level, no leaks ever and haven't done any brake work so not sure how that would have changed. Any other thoughts?

Sun Sep 21, 2014 4:02 pm

rkoss wrote: (1980 Westy)
I have sort of a reverse issue. My light doesn't stay on. It will intermittently flicker at a certain reach while using the foot brake. I have never had an issue before, it just started on my last trip.

So while driving, applying brake at high speed, it sometimes flickers on. If I maintain the position of the brake pedal when I see it come on, it may stay on a few seconds. It does not come on consistently every time I use the brake. Always at random an only a quick flicker. It functions properly with the hand brake and turns off when I release the park brake.

I am getting a sense that there's a fluid level sensor in this system from some previous comments? Ill check my fluid level, no leaks ever and haven't done any brake work so not sure how that would have changed. Any other thoughts?

Maybe my comment wasn't clear, I suppose.

The Hand Brake Light beside the cluster only come on when I applied the foot brake. It was like yours at first... just occassionally a flicker. But, it eventually would come on bright every time I applied the brakes.

It's your switch. There is no brake fluid level sensor in an 80 model Vanagon.

Mon Sep 22, 2014 5:20 pm

Ah hah, yes, I definitely think it's a bad/incorrect run of switches.

I had the same problem (warning light on except when brake pedal pressed) after replacing my switches over the weekend.

This thread saved me a few hours of troubleshooting. I swapped the pins in the connectors, and all works as it should now.

The new (and wrong) switches are by SKP, p/n 113 945 515G. Other than the wiring being different, they appear to be of good quality.

Thanks cybervette!

Robyn

Wed Sep 24, 2014 8:31 am

Small payback for all the hours of frustration these threads have saved me! Glad this helped.

Sun Jan 29, 2023 11:37 pm

Removing the seatbelt warning may cause the brake warning light to remain on. My 87 Vanagon had brake warning light that stayed on after ignition on. I think my seatbelt warning was removed by previous owner. The harness has wires for both the seat belt warning and brake warning. I removed the brown wire from pin 1, which was part of the seatbelt warning system, and now my brake warning light works perfect.