Emergency Brake light on dash stays on

[txasylum]

On my 1974 Super, the dash light for the emergency brake (hand brake) stays on even when the hand brake is disengaged. If I tap the brake pedal it goes off. Sometimes it stays off, other times it comes back on when I release the foot pedal.

Could one or both of the brake light switches on the master cylinder be the cause of this problem?

Thanks
Bob

[kreemoweet]

No, according to the '74 wiring diagram, the parking brake warning light is not
connected to the brake switches/warning light at all.

EDIT: Sorry, not true, I was looking at wrong wiring diagram.
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[Tim Donahoe]

The brake-still-on switch at the handbrake could be wonky—assuming you still have it.

If not, on my 1974 Super Beetle, I recently had the same issue. The brake light was staying on longer, going out, then coming back on. After driving and braking a bit, the light would go out. Like you, I thought it was an mc brake switch. In a manner of speaking, it was ... because it wasn’t faulty, it was just doing it’s job.

One of my rear drums was also getting much hotter than normal. As it turned out, the wheel cylinder was frozen, and the shoe was pushing against the drum—all the time. After replacing both rear wheel cylinders, the light went out as normal.

Apparently, the master cylinder switches also register uneven brake pressure.. or, that’s my theory, anyway; because, in effect, one rear brake cylinder was frozen, I replaced the offending cylinder, the light never came on again, except for initial start up (like it should).

This was a month, or so ago. No more brake warning light staying on, since.

Tim
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Richard O'Brien

[txasylum]

Yeah, I know. Doesn't make sense to me how just touch the brake pedal cause the dash light to go out.

[txasylum]

I've replaced the entire rear brakes, drums, slave cylinders. Did not change a thing. I did that because it needed it, not because of the light on the dash.

[ashman40]

[txasylum]

Wow! Thanks for the very detailed instructions to chase this thing down. I really appreciate it. I am going to print this off and follow your instructions. The problem is that I am going out of town tomorrow, so it might be a couple weeks before I can trace this down. But I will and let you know what I find out.

Bob

[Tim Donahoe]

Did you also replace the rear soft lines when you did the rear brake job?

Tim
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Richard O'Brien

[txasylum]

No, I only replaced the drums, brake shoes, hardware (springs, etc.), and the slave cylinders. I inspected the brake lines and they looked good (not wet or leaking).

[txasylum]

So I started to mess around with this issue today. I decided to check the wiring on the master cylinder. When I disconnect the brake switch connection closest to the firewall the light goes out. That did not do the trick, but I decided to check how tight the switch is on the car. I was able to tighten it up another two or three more turns. That seemed to help, meaning the light was staying off longer, but it still came on. So I decided to order a new switch since they are cheap enough. We will see.

[ashman40]

[txasylum]

So, it seems I was having problems with the front switch only. With the rear switch (closest to front) connected, I disconnected the switch closest to get to the firewall. The light went out. I'm guessing that was the bad one. I ordered one switch only to change it out. From your post, is it possible the MC is bad? I am getting pressure to all four wheels when stepping on the pedal. If it means anything, the break lights work as they should, meaning they only come on when the break pedal is applied.

[ashman40]

Did you check the wiring at the brake switch boots? If the boots are wired wrong you cold have the same issue even with a working brake switch.

Test the switch and test the wiring. Look at the above diagram and you can see that the switch closes the opposing contacts when you step on the brake pedal. Use a test lamp or MM and test the switch.
Also, you can see that #81 and #81a are connected together when the switch is NOT pressurized. Confirm this is the case.

Test the brake switch plug. First make sure the correct colored wires are in their proper place on the boot (bottom right diagram). Test that with the ignition ON there is 12v on the black #82a wire.
Using a jumper wire connect #82a to #81 and the rear brake lights should turn ON.
Move the jumper wire so #81 and #81a are shorted together. This simulates a failed brake circuit. With the other brake switch connected to its plug and the ignition switch ON, step on the brake pedal and the Brake Warning lamp should turn ON along with the rear brake lights. This confirms that plug is wired correctly. Swap to the other plug and run the same tests.
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AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[txasylum]

Thank you all for the information. Yes, I did check the wiring, but suspected it was one of the two brake switches. So I ordered one, put it on and problem solved. IT was a bad brake switch. Glad it was that easy, sort of.... LOL