The Stovebolt Site Forums The Shop Area The Electrical Bay Brake lights

55.2 Chevy truck.
The brake lights, and blinkers work fine until I turn on the headlights. Then, the brake lights stay on bright, no blinkers, just a full bright light.

Any ideas?

wires on the light switch wrong? note that the headlight wire on the switch is blue and there are blue wires on the signals for the front, maybe you have those connected wrong at the plugs near the rad - are the park lights on with the headlights? the brake lights get power from a terminal [black wire] on the switch, but there should be no connection between the brake circuit or the park light circuit and the headlights

Bill

I took out the light switch and examined everything. It's hooked up correctly but I did notice there is no orange stoplamp wire for the "S" terminal. Though the brake lights do go on when I depress the brake pedal with the headlights off. The "headlight group" on the wiring doesn't have an orange stoplamp wire. Could that be the problem?

The front park lights go on in the park light position, then go off when the headlights are on. The back lights are very bright with the headlights on.

what color wire takes power to the brake light switch? should be orange [white on the other terminal goes to brake lights] .... maybe both filiments in the rear lights are on at the same time to be 'very bright'? sounds like the tail light circuit is over-riding the stop light circuit when the switch is on .... I'd say you have something mixed in the plugs under the drivers floor [sketched at bottom of signal diagram]

Bill

One of the wires is orange and the other is white at the brake light switch. Shouldn't there be an orange wire hooked up at the "S" terminal on the light switch? If so, where does that go?

You're right, it seems that both filaments are lighting up.

This is a bummer, I was so careful when wiring this up, now it looks like I need to unwrap the wires to see what I did wrong. At least I can drive it during the day!

the orange wire at the light switch is the one that should go to the stop light switch .... track it back and see what it's hooked to, an ohmeter will do it, with a long wire for one lead clipped to the stop switch end, no need to unwrap things - have the battery disconnected ... but check those plugs under the floor, it's a confusing arrangement there with the signals added in

Bill

Hy jomichael, are your tail light housings well grounded, that is just one more thing to verify. You could check the ground circuit with the ohmeter squeeze mentioned, with a long lead back to the battery or a known good ground, hope that helps.

If that orange wire indeed does go from the light switch (which is missing) to the brake switch, then why do my brake lights work with the headlights off?

Can I simply pull that orange wire off the brake switch, and add a new one from the brake switch to the light switch?

I'll go pick up an ohmeter and track that wire down later today. Been getting "the hairy eyeball" from the wife cause I'm working on the truck too much lately!

the stop and dome terminals on the light switch are not affected by the switch position, always hot .... the orange wire on the stop switch has to get power someplace, maybe the fuse panel if you have one .... yes, I'd think you could change it to match the diagram, but you should find the other end of the orange wire first

Bill

The orange wire from the brake switch goes to the fuse panel.
I swapped out my light switch for another one I had laying around and for some reason things changed. Now, when the headlights are on the brake lights are off except when the brakes are depressed. I guess that is a step in the right direction. But it seems like the brake lights are on the filament that is less bright. Also, when the headlights are on, should there not be parking lights on at the brakes?

Even in the parking light position only the front park lights come on. Shouldn't the back?

BTW, I did take some wire and run it as the diagram showed (bypassing the fuse box) and the brakes lights didn't work at all. I spliced in that original orange wire and the light lit up so obviously I need that wire.

Very frustrating this wiring stuff.

sounds like you have some wires still crossed, the tail lights ['rear park lights'] should be on with the headlights and with the front park lights [first notch of the switch], and they're the dimmer filament, the brakes go to the brighter filament .... check the color codes again! especially on the switch - black to tail

Bill

When I rewired my 55.2 I had a devil of a time with the rear lights. I found that everything was grounded to the bed and the bed was not grounded to the frame. I ran a wire from the bed to the frame and fixed my problem.

As 3B asked earlier - are your tail light housings well grounded?

I finally figured it out. I went through all the wires and they were all going to the right places. So in desperation I created a chart and labeled what was on and what was off in the various light switch positions, as well as what filament was lighting up. What stood out from the chart was that the rear parking lights were on the bright filament which means the blinkers won't work and the brake lights won't work. So I flipped the wires at the rear lights. The two black wires were connected to the colored wires (the white ones in your diagram Bill) and everything works fine now. I must have installed the wiring harness to the rear light housing incorrectly (these were reproduction tail lights and harnesses). Though it seemed like it could only go in one way.

Long story short, 8 hours of frustration and a 5 minute fix! Gotta love this hobby!

Hy jomichael, I'm glad you found and fixed the problem, thanks for letting us know what was wrong.