Brake switches wiring issues at master cylinder

[herbie13]

I have a '69 type 1. The master cylinder is the newer, two switches with three prongs. I had my cars wiring harness replaced. The wire colors at the master cylinder do not all match the original wire colors; some do. I have verified that the RED wire goes to the brake warning switch/light, that the BLACK w/RED goes to the tail lights and that the BLACK goes to the fuse panel.

Because of wire color issues, and not being able to determine absolutely, that the other connecting wires (i.e., not the RED, BLACK w/RED, BLACK) are wired correctly, I have made three "Y" wires to replace the harness wires for trouble shooting purposes.


What I have done: connected the RED wires to center post 81a, connected the BLACK w/RED to outer posts 82, connected the BLACK wire to the other outer post 81.

RESULT:
Turn the ignition on and brake lights come on without pushing the brake pedal.
So, I switched the 81 & 82 wires on one switch. The brake lights now come on when the pedal is pushed.

PROBLEM:
The brake warning light comes on and stays on when the engine is running, even after I disconnect the RED wire from both brake switches.

I must be missing something, but I'm not figuring it out. Can anyone shed some light on what it is, or what I'm doing wrong?

Thanks in advance.

[VERTED71]

Someone will correct me if I'm wrong but, I think the brake light switch is a indicator of the switch not working correctly or shorting. Do you have functioning brakes or just brake lights and the indicator still on?

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[ashman40]

This diagram from Speedy Jim's site should answer your questions:

(click the image to increase size)


Something sounds wrong with your descriptions.
Disconnect all wires.
With a test lamp identify which of the three colored wires has 12v+ when you turn the ignition switch ON. It should normally be the black (#15) wire which comes from the fuse box.
Connect this 12v+ source to each of the other wires (black/red and red) one at a time. When you connect it to red, the Brake Warning Light in the dash should turn ON. When you connect it to black/red the rear brake lights should both turn ON.

Using the above diagram as a guide, connect the correct wires to just ONE of the switches. Leave the other switch disconnected and make sure any extra wires are NOT touching chassis ground. The 12v+ source wire (normally black) should be connected to the #82a terminal. The black/red wire to the rear brake lights should connect opposite on the #81 terminal. The red wire to the brake warning light should connect to the middle terminal (#81a).
With the wires connected to just the one switch, turn the ignition ON and press on the brake pedal. The rear brake lights should turn ON.
Move the connections to the other brake switch leaving the original switch disconnected and repeat the test. You should get the same results.

If both switches work independently, connect both switches in the identical fashion. The problem you had after you moved the wires around was that your two switches were wired differently. BOTH switches must be wired the SAME.

As a temp fix, you could disconnect the red brake warning switch wire from both switches. As long as the remaining two wires are connected opposite each other on BOTH switches the brake lights should work. But you will not have a working brake warning lamp.

Run the tests and report back your results. This is important so that others who follow you can learn how to fix the same problem on their car.
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[herbie13]

Thanks for your responses. First, yes there are brake lights and brakes. Second, my 12v test light has crapped out. Will have to wait until tomorrow to get a new light bulb or test light to finish the tests. Will get back tomorrow.

P.S.
I have tested both brake light switches and they work individually.

[kreemoweet]

By your description, it also seems your brake warning lite is miswired. If the red wire is disconnected at the switches,
there is no way the warning lite can come on, presuming correct wiring. The brown (ground) wire should be on the
center (bulb holder) tab, the red wire on the "K" tab, and a black wire (from the ignition circuit) on the "15" tab.
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[herbie13]

Thanks to ashman40. Your description about what each of the three primary wires should do was the most helpful.

The BLACK (power), BLACK w/RED (brake lights) and RED (warning light) and how to verify their source, i.e., what I should see when I connect each to +positive power, was what I wasn't getting.

So, my brake light switches both work, and my brake lights come on correctly, as well. I verified (with great difficulty) that the warning lamp was wired correctly. Now, however, the warning lamp isn't coming on at all. I even purchased a new bulb; no difference. The warning lamp holder may now be non-functioning, but I'm not about to go finding and replacing it. A good, used one is selling for $30; and that's without the colored lens or collar.

A big thank you to all.

P.S.
I've checked all four (2 on the MC, of course) of my brake light switches for any identifying marks or connection markings and can't find any on any of them. My point here is that the numbering of the switch terminals isn't useful for trying to make the connections.

[kreemoweet]