Brake Sensor?

Lurch830

Lurch830

messin' with sasquatch
Joined
Mar 1, 2007
Location
Wilton, NC
I posted in my C30 thread, but figured I'd get some more visibility here...does anybody know what this does?
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Its on the brake splitter/proportioning valve on a 1972 C30 and the wiring connector looks like a mini spark plug boot. I haven't traced the wire into the cab yet (hoping to tonight/tomorrow), but I know my new wiring harness doesn't have anything like it and the instructions don't mention it anywhere.
 
Yep it grounds the brake warning light if you loose half the brakes (front or rear)
 
skyhighZJ said:
It’s for the Brake dummy light on the dash
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Tim C said:
Yep it grounds the brake warning light if you loose half the brakes (front or rear)
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Thanks! I figured it had to do something like that, but this is exactly what I needed to know! I'll probably pull a new wire into the cab and solder to the plug since I don't have a new connector.
 
FYI it should also tee off and go to the ignition switch to a terminal that goes to GROUND in start to bulb check the brake light. There is a second grounded in start terminal on the switch that bulb checks the temp warning light if used or will peg the temp gauge when starting on some trucks.

You can tee into that wire also and add a switch to the parking brake mechanism if you want so the light will come on with parking brake like a new car if you want to. They did not do that factory.
 
Tim C said:
FYI it should also tee off and go to the ignition switch to a terminal that goes to GROUND in start to bulb check the brake light. There is a second grounded in start terminal on the switch that bulb checks the temp warning light if used or will peg the temp gauge when starting on some trucks.

You can tee into that wire also and add a switch to the parking brake mechanism if you want so the light will come on with parking brake like a new car if you want to. They did not do that factory.
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The brake light does light on start so that part at least is working. Any way to test the sensor?
I've never seen the temp light come on or the temp gauge even move. Grandpa removed the temp sensor when he overhauled the block & never put it back. I've added one and will wire it this weekend if everything goes according to plan. I'm guessing the R lead goes to the light & the S lead goes to the gauge?
I like the idea of the brake light as an indication the parking brake is on...I'll add that to the to do list!
 
If you're talking about the r and s terminals on the starter solenoid no. R is resistor bypass and goes to the coil to give it full power while starting, the s terminals goes to the ignition switch and is hot while cranking. The ignition switch in the dash will have 2 terminals that go to ground through the switch body and dash in the start position too. One goes to the brake light on the dash the other the temp light. If you have a gauge you probably won't have the light too, you can ignore that terminal. Some Chevy trucks teed the temp wire to the ignition switch whether it was a gauge or a light and you'll notice the gauge peg when starting because it goes to ground. That's not necessary, gm did it so they didn't have to make two different dash harnesses.
 
Tim C said:
If you're talking about the r and s terminals on the starter solenoid no. R is resistor bypass and goes to the coil to give it full power while starting, the s terminals goes to the ignition switch and is hot while cranking. The ignition switch in the dash will have 2 terminals that go to ground through the switch body and dash in the start position too. One goes to the brake light on the dash the other the temp light. If you have a gauge you probably won't have the light too, you can ignore that terminal. Some Chevy trucks teed the temp wire to the ignition switch whether it was a gauge or a light and you'll notice the gauge peg when starting because it goes to ground. That's not necessary, gm did it so they didn't have to make two different dash harnesses.
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I was referring to the new temp sensor I installed for the R & S leads. Its supposed to have one lead for a gauge & another for a light. I'll probably add an 'idiot light' to catch someone's eye in case I'm not driving it and it starts running hot.
 
Gotcha, I'd never seen that before
 
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