brake light issue

[stunter2boy79]

first off i replace stock proport valve with this one http://www.summitracing.com/parts/WIL-260-11179/ . i hook up the factory brake light switch wire to one of the connector ends, and i grounded the other connector end straight to the battery. now with the head lights off i step on the brakes they light up. i shift (manual) to reverse and no reverse lights. turn the head lights on, i step on pedal and the rear lights go off and the reverse lights come on. shift to reverse and still no reverse lights. now is the ground to the batt the bad problem or what else could it be?

 

[zombie1969]

Unless you connected that switch to power by mistake you have a separate problem.

 

[Fordum]

I'm not sure where to start. First, what year is this truck? Its been a long time since I saw a pressure type brake light switch. I think they have all been running off the brake pedal since they came out with the split master cylinder.

That switch should be the brake system failure light. It should not be hooked up to the brake lights I don't think.
Did you mean you hooked up the brake failure light to it, or your rear brake lights?

And the reverse lights should have nothing to do with the brake lights.
But, a bad ground to the rear lights might cause that problem.

However, if you hooked the brake light switch wire from the pedal to that switch, then that is your problem. When the brake is pressed, the brake light switch wire receives 12 volts, not ground.

But, don't just hook 12 volts up instead of ground until you reply. I'm not sure enough of what you did to say do that yet.

 

[stunter2boy79]

its a 1980. i took the wire that went from the stock proportioning valve and hook it up to the new valve. read on here the stock valve was grounded by being on the frame. the new valve isnt on the frame so i hook up a wire to ground it and grounded it straight to the batt.

 

[Fordum]

OK, that helps. I'm not familiar with that valve, but it sure looks like the correct way to hook it up.
If that switch is just a single pole single throw like it looks like it is, then you did right.

Of course, you could disconnect it briefly to make sure that the problem does not go away, but I'm pretty sure that it won't.

I'm betting now on a bad ground. Either a general body ground, or one specfic to the rear lights.

I think that where the harness from the front of the truck splits to go to each side of the rear, right behind the last rear cross-member or bumper, there is a ground wire that is attached to the frame.

You might crawl under the back and check that harness for a disconnected wire.

 

[stunter2boy79]

thank ya sir. i was thinking a ground issue also. i shall crawl under there tomorrow while at work n check it out

 

[496truck]

Problem. The wire that goes to the prop valve is for the brake malfunction indicator in the dash. It has nothing to do with the brake lights in the rear of the truck. Those are operated by a switch on the brake pedal under the dash.