Brake lights not working

[simone0414]

I believe this is my first post on this forum but I have been a member of the other forum for sometime. So hello to everyone.

Ok, having a problem with my brake lights. The third light works but the 2 in the back don't. I had this problem a while back & it was a blown fuse in the fuse block under the hood. I think it was the fuse for the signal lights. Have read that power for the lights in the back goes through the trun signal somehow. Anyway I checked all fuses in the fuse block & in the cab & all are good. I have the problem narrowed down( I think) somewhat. I pulled the brake relay in the fuse block & jumped it with a paperclip. The brake lights came on. So this means that everything from the relay back to the brake lights is ok. But I am not getting any power to activate the relay when I push on the brakes. ( checked with mulitmeter). So I thought it may be the brake light switch so I replaced that & still no lights. So I checked to see if power was getting to the mini brake fuse in the cab. Again checked it with my multimeter. No power on either pin. So I turned the ignition on & now I do get power. Shouldn't that fuse be hot at all times? If not how do the brake lights come on when the truck is off?

So I took bottom part fo the steering column off to check out the turn signal switch. I noticed that one of the wires to it is about 3/4 pulled out. It is a light blue wire. Looks like 16 gauge. It's still in there but not by much. I have no idea if it goes to the brakes but it is soemthing i need to fix. There's not enough room to repair it without disconnecting it from the turn signal switch & I tried to take it out but again not enough room to work. Looks like in order to get it out I will have to take the top part of the steering column cover. I've never done that before & I am afraid to take enything more off the column for fear of activating the air bag.

I've tried to trace wires so I could see where I have power & where is stops but there is no friggin room to see or get a test light in. That bad wire could be the problem but I can't trace it back without tearing half the dash apart. I don't understand this system well enough either to know what to be checking & what to be looking for.

If someone could give me some suggestions on what to do from here and or explain how this whole system works then I probably could get it.

 

[Turbine Doc]

Welcome too THE 6.5 information resource;

IMO fuse for brake lights blown or bad gnd, 3rd light is independent of brake lights.

Usually happens when a trailer has been hooked up that has poor gnd and fuse pops with extra draw of the trailer lights.

 

[Turbine Doc]

Have you checked the fuse holder terms seeing that you checked fuse already

 

[Turbine Doc]

You recently try to add a brake controller ?? blue wire generally is the power for that controller

 

[Turbine Doc]

can you grab pics I'm away from my manuals so will need some pics of what you are describing

 

[simone0414]

I forgot to mention that I do have a brake controller but I did not install it. It was on there when I bought the truck. That has been acting funny as well. Sometimes the little light on it will come on green & stay on, even with the truck off. Eventually it will go out on it's own. Only seem to do this after it has been cold outside & then we get warm temps. Something else that is not right. There is a blue wire that goes out to the fuse block. Joins onto a wire right before the fuse block. Is this the wire that goes to the relay to activate it? There is also a black wire for ground. I checked that & looks ok. There is a red wire & at least one more( can't remember color) that goes from the brake conrtroller. Could the brake controller be stopping the power getting to the realy somehow?

I can get some pictures if necessary but not until tommorow.

 

[Dan Hunter]

Welcome too THE 6.5 information resource;

IMO fuse for brake lights blown or bad gnd, 3rd light is independent of brake lights.

Usually happens when a trailer has been hooked up that has poor gnd and fuse pops with extra draw of the trailer lights.

I had that happen. It also sacked the cruise control. Got home and stuck a new fuse in it. Fixed the ground wire. Everyone happy.

 

[Turbine Doc]

. Could the brake controller be stopping the power getting to the realy somehow?

I can get some pictures if necessary but not until tommorow.

Pics yes, brake control fault yes, as it could be shorting the circuit, whos brake control, Prodigy ???? can you unplug it and check the brakes

But Gnds on GM's notoriously poor, check them also

 

[chrisk1500]

Crawl under the back of the truck and look for broken/corroded wires in the light harness.

This is something we do yearly with our OBS trucks....gravel roads are a killer...

 

[simone0414]

The brake controller is a Voyager /technosat.

I was going to check the wires in the back but once I realized that the lights worked at the relay then I figured everything from there back is ok.

 

[simone0414]

I found the problem. The splice had come apart where the brake controller was wired into the power wire to the relay.

Thanks for everyones advice.

 

[Turbine Doc]

Great we love to hear success stories