Wiring brake imbalance switch

[Blue71]

I went from stock brake proportioning valve to an aftermarket one. The stock one has two wires from stock harness that lead to the pigtail cap on the warning switch and the new cap with pigtail only has one wire. So have two wires coming from original harness to hook up to one wire from new brake warning switch. How does it need to be wired to work correctly?

Thanks a bunch,

Andy
Blue71

 

[DirtDonk]

I should remember exactly, since I've not only read it here many times, but also have done at least one in the past six months. But I only "think" that you tie the two wires to the one. It's just connecting in a different way now.

You can test it to make sure of course, because it's possible that you could utilize only one of the original wires and still have it work. Or you can twist them as a pair and connect to the single wire that way.

I just don't remember if both methods work, or only one. You might be able to find some of the old threads here that discuss it. Or you can wait for someone with a better memory to chime in.

Paul

 

[DirtDonk]

Ok that's it. You have to twist the two together and connect to the one.
That way you still have your power from one lead, your "proof out" (when the ignition switch grounds the lead during START only) through the other, and then the temporary ground when the switch trips due to some brake fault.

Paul

 

[Blue71]

Paul,

Thanks so much...gonna "get my tie on" and tie them together.

Thanks,

Andy
Blue71

 

[DirtDonk]

Gonna use some household wire-nuts then, eh?
Heck, I've seen stranger things on EB's, and that'd sure be an easy way to get 'er done!%)

But I think we should sic Viperwolf1 on this to clear something up.
I can see how it would function properly under normal conditions. That would be light the lamp on the dash only while the key is in the START position, but what exactly does it do when you have a brake fault and the little shuttle piston activates the switch?
Seems like that would be power to ground, which is a short-circuit. And with no fuse protection, what's up with that!

Anyway, maybe one of the others that have used this method can chime in on how it works. Maybe the switches themselves have some sort of resistor in them to keep it from becoming a direct short to ground? I dunno, but that would 'splain a few things.

Sorry, but I just couldn't let it go. I know many others have said to do it this way for the past few years, but the more I think about it, something just doesn't seem right.

Paul

 

[Viperwolf1]

You got it right Paul. The 2 pins at the stock switch are actually tied together. This switch and the ignition switch proof terminal are both on the ground side of the circuit. If either one goes to ground it completes the circuit and causes the light to illuminate. No need for a resistor because the bulb is acting as the resistance.

 

[DirtDonk]

Ahhhh, yes. Forgot all about the bulb!

Thanks Phil. Appreciate the clarification.

Paul