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Posted by: dennisphelan Jan 28 2019, 12:56 PM

The large red brake warning light on the combo gauge is flashing. The emergency brake is disengaged. I checked the brake master cylinder and the one wire ( it only has one connection) that goes to it is attached. It appears I have some fluid leaking as the connection was wet with fluid. The car hasn't been driven in 12 years so I am sure many things could be wrong. What is the switch on the master cylinder sensing?

Thanks,

Dennis Phelan

Posted by: 914_teener Jan 28 2019, 01:47 PM

A failed MC. So it is probably rusted and the light is doing what it is supposed to.

Edit:

Or switch is rusted. You don't mention if the brakes work....have a peal and stop the car or not. Need lot's more info.

Good Luck.

Posted by: Spoke Jan 28 2019, 02:04 PM

The MC switch should have a small reset button on it. If it doesn't, disconnect the wire to the switch and see if the flashing indicator goes away. As mentioned, if it is the MC switch, you need to make sure the MC is in good working condition.

Posted by: 914Sixer Jan 29 2019, 11:02 AM

If you need a new switch let me know.

Posted by: pvollma Jan 29 2019, 11:21 AM

When I first picked up my new-to-me 76, the light would continue to flash after releasing the handbrake. I found that pulling it up again and then forcefully pushing it down with the release button pressed would cancel the warning light. The PO had let the car sit for a long time while he worked on it, so I suspect something in the switch that senses the handle position was hung up or corroded. After a few weeks of using this method, it was no longer needed, but, of course, YMMV.

Posted by: lierofox Jan 29 2019, 05:06 PM

I wanna say the switch is a "low pressure light" where the brake master cylinder gets depressed too far without making enough pressure. How's the pedal feel?

When I got my '75 the warning light was always on, as part of the process of going through everything and redoing the brake system I ended up replacing the master cylinder just to be on the safe side, it also had a warning light until I reset the button. Once I replaced the MC and bled the brakes it never came back again.

Posted by: Dave_Darling Jan 29 2019, 06:26 PM

The light flashes when one of the brown/white wires that goes to it gets shorted to ground. The two wires go to the brake warning switch in the master cylinder, and to the button under the handbrake handle.

If the handbrake handle doesn't press the button under it down, the wire going there will be shorted to ground. If the switch in the master cylinder detects a massive loss of pressure (e.g., bleeding the brakes) it will close until the reset button in the switch is pressed.

If one of the wires to those falls off and lays on the chassis, that can cause it to be shorted to ground. That will also make the light blink.

But the most common thing is that you bled the brakes and didn't press the reset button on the master cylinder switch.

--DD

Posted by: dennisphelan Jan 30 2019, 02:27 PM

Thanks for the reply.

Posted by: 9fourteen14 Aug 12 2019, 04:30 PM

Mark i might need a switch... if not an entire new Master Cyclinder... but my brakes seems to work fine.

ummm

Niece


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Posted by: 914Sixer Aug 13 2019, 10:27 AM

Here you go, used but good condition. Reset button works. $20 shipped.



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Posted by: jcd914 Aug 14 2019, 01:50 AM

Disconnect the wire from the switch on the master cylinder and see if that stops your flashing brake light. Make sure the wire doesn't ground against anything.
If not make sure your hand brake lever is all the way down and pushing the switch.
If still not, unscrew the brake lever switch and pull the wire out enough to make sure it isn't grounding against anything.

The brake warning light is triggered by grounding the circuit at either the master cylinder or the hand brake switch.

If neither of these wires is grounded and the light still flashes there is a short to ground somewhere in one of the wires.
Some cars had a third wire for a brake fluid level switch, near the brake reservoir.
If your car has the extra wire it could be grounded and causing the light to flash.

Jim

Posted by: 914_teener Aug 14 2019, 09:56 AM

So ......admins.....Ii didn't post this. Very weird.