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Old 10-24-2011, 12:25 PM
catch2otwo catch2otwo is offline
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brake light switch

When i step on the brakes in my 72 wag the brake lights do not illuminate. I looked at the brake pedal assembly and didnt see any kind of push button switch. I see two wires coming out of the bottom of the master cylinder. Is that some kind of pressure/hydraulic switch for the brake lights?
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Old 10-24-2011, 12:30 PM
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Take a look at your master cylinder, there should be a hydraulic switch threaded into the underside of it. You will have to bleed your brakes if you replace it.
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Old 10-24-2011, 01:21 PM
catch2otwo catch2otwo is offline
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Quote:
Originally Posted by mattywilz
Take a look at your master cylinder, there should be a hydraulic switch threaded into the underside of it. You will have to bleed your brakes if you replace it.

Thats exactly what I thought that was. Do these usually go bad?
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Old 10-24-2011, 01:43 PM
oldyellowwagoneer oldyellowwagoneer is offline
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Probably the factory switch so I guess they don't go out too often.LOL
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Old 10-24-2011, 01:55 PM
joe joe is offline
 
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Quote:
Originally Posted by catch2otwo
Thats exactly what I thought that was. Do these usually go bad?
In forty years? Yes. Changing brake fluid yearly as you should goes a long way to making the hyd parts last.
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Old 10-25-2011, 09:10 AM
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My 69 had the same MC brake light switch. When it gave up, it not only leaked brake fluid, it let air into the MC. Plugged the hole and mounted a switch on the pedal, where it belongs. One example of bad design creating a completely unnecessary safety risk.
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Old 10-25-2011, 08:27 PM
catch2otwo catch2otwo is offline
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Quote:
Originally Posted by lkmarsh
My 69 had the same MC brake light switch. When it gave up, it not only leaked brake fluid, it let air into the MC. Plugged the hole and mounted a switch on the pedal, where it belongs. One example of bad design creating a completely unnecessary safety risk.

Any picture of the switch you used?
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Old 10-25-2011, 09:22 PM
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Just test the switch first using a test light - as it could easily be a bad ground or break in the wire or connector. It's a 2 wire switch and are used on many GM cars. Cheap part buy messy to replace.

I would remove the 2 wires bullet style connectors, clean the contacts and test first.
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Old 10-26-2011, 07:39 AM
catch2otwo catch2otwo is offline
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Quote:
Originally Posted by blakeusa
Just test the switch first using a test light - as it could easily be a bad ground or break in the wire or connector. It's a 2 wire switch and are used on many GM cars. Cheap part buy messy to replace.

I would remove the 2 wires bullet style connectors, clean the contacts and test first.

Wow brain fart, I just realized that since my wheel cylinder has been leaking, my mc is empty. And since the switch is a pressure switch, there would be no pressure on the switch. I was just about to ask how to test it, and put 2 and 2 together.
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Old 10-26-2011, 07:46 AM
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Quote:
Originally Posted by blakeusa
Just test the switch first using a test light - as it could easily be a bad ground or break in the wire or connector. It's a 2 wire switch and are used on many GM cars. Cheap part buy messy to replace.

I would remove the 2 wires bullet style connectors, clean the contacts and test first.

Don't need a test light, the truck is already equiped with one. Just touch the two wires together and see if the brakelights come on.

Oh, and the pressure switch is more of a Ford deal. General Mayhem has been using pedal mounted switches for over 60 years.
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Old 10-26-2011, 07:50 AM
catch2otwo catch2otwo is offline
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I will try connecting them two to see if I get power through the wire. Thanks
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Old 10-30-2011, 08:12 PM
catch2otwo catch2otwo is offline
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OK so I unplugged both wires coming from the MC pressure switch. Connected them together. Put my test light on the wire and got nothing. To confirm, I turned on the headlights and the same wire became live.

Did I do something wrong or is my wiring fubard? My friend said the brake lights worked when he parked it so whats my next step? I looked at my jeep service manual but there was no wiring schematic.
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