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Unread 01-09-2010, 08:55 PM   #1
checkman808
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Converting Brake Pressure Switch from 2-Wire to 1-Wire Configuration

Does anyone know how to wire a single-wire Brake Pressure Switch in place of a 2-wire switch? I replaced my 81 CJ's stock Proportioning Valve with one calibrated for use with rear disc brakes. The stock P-valve was a 2-wire configuration, the new one is a single-wire config. The tech from the company I bought the P-valve from said to wire one line to the switch and the other to ground. Depending on how I wire it either the Brake Warning light stays on all the time or it doesn't operate as it should when the ignition is turned on or the parking brake engaged. I appreciate any assistance. Chucke

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Unread 01-10-2010, 03:33 PM   #2
HackFabrication
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You need to splice the two wires together:


I don't recall, offhand, which of the two I spliced into the other, so you'll need to get a test light and check which one works when you twist the key to start (this is where the light is 'tested'). That the one you want to splice into the second wire.

The other wire will not light unless it's directed to ground (when the brakes fail), so that's the one that gets connected to the combo valve switch.

I know if I've got this bass asswards, someone will help out (John???).
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Unread 01-11-2010, 04:40 AM   #3
John Strenk
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Yeah. When you have only two wires and you splice them together. it doesn't really matter which one get's spliced into which.

You should be able to just splice the two wires going into the combination valve together. One wire runs to the warning light. One wire runs off to the ignition were it gets grounded when the key is turned to "start" to check the circuit is working and that the bulb works. Did they give you a plug to fit the switch on the combination valve?

I have no idea what the tech was saying. I think he was just guessing on what the two wires might possibly do.
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Unread 01-11-2010, 06:04 PM   #4
checkman808
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Hack, John, Thanks for the post, you both were spot-on. This confirmed what I thought was the case after pouring through the schematics, but it wasn't working when I tested it... Turns out my little blue plastic tap connector wasn't connecting on one line or the other.... I verified it with jumpers and an ohmmeter and replaced the connector and it works perfectly...

To answer your question John, they did not supply a plug until after I called them to ask about it... "oh yeah! you'll need this $13 plug." Actually a drop in the bucket considering everything else I've done the last 10 years on this one. Thanks again guys, Cheers!

Chucke
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Unread 01-12-2010, 11:22 PM   #5
HackFabrication
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Quote:
Originally Posted by John Strenk View Post
it doesn't really matter which one get's spliced into which.
Yeah, I couldn't remember all the ciphering and crawling around I did on this 'issue' when I was confronted with it. I do recall that somewhere between the second and third case of beer (over a two week period), I figured it out.

What a head slapper that was......
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