Wiring Issue - Brake Lights (72 C10)

[devildriver6]

Okay, I could use some help here.
First off, let me start off by saying the wiring in this truck could use some tidying up.
That is to say....it's a mess.

So, here's the issue: all lights work, including turn signals, flashers, headlights, markers, etc.
The ONLY thing not working - brake lights. I swapped out the switch, no luck

Fuses are all good. Brake switch is new. Wiring all seems okay.
I'm not a wiring guy (yet...lol...this truck will turn me into one, I'm sure).

Any clues on where to start?

[4x4 k1500]

Did you use a tester to make sure you have current on both sides of the brake
switch when pressure is applied to the brake system?? Just because your brake switch is new doesn't mean it's good. Turn signal and brake lights use the same bulb element

[Peanut74]

As stated above do a continuity check on the switch to make sure it's good. If the switch is good check the wires are good. Do that by checking each wire to see if you have continuity to ground.

Hope this helps narrow it down for you.

[RustyPile]

I see you've been a member here for a good many years, but seldom post. You may not know that we have an ELECTRICAL forum where you can download wiring diagrams. Follow this link and download the proper wiring diagram for your truck.

http://67-72chevytrucks.com/vboard/f...splay.php?f=64

It will be a great help in troubleshooting electrical problems. In the meantime, here's some tips to help you get started..

Using a voltmeter or 12V test light, check both sides of the brake light fuse for voltage. A visual inspection isn't the proper fuse test. Sometimes rust accumulates on the fuse box contacts causing bad connections. If you have voltage on both sides of the fuse, disconnect the plug at the brake light switch and check for voltage on the orange wire. If no voltage is present, check the wire for breaks or disconnects. If voltage is present, jumper the orange wire to the white wire. If all circuits are working, you should have brake lights. If the brake lights now work, the switch is either bad or needs adjusting. If the brake lights don't work with the jumper installed, check for continuity of the white wire through the "half moon" turn signal harness connector.. If there is voltage on the turn signal switch side of that connector, you probably have a bad turn signal switch.

[devildriver6]

Originally Posted by RustyPile

I see you've been a member here for a good many years, but seldom post. You may not know that we have an ELECTRICAL forum where you can download wiring diagrams. Follow this link and download the proper wiring diagram for your truck.

http://67-72chevytrucks.com/vboard/f...splay.php?f=64

It will be a great help in troubleshooting electrical problems. In the meantime, here's some tips to help you get started..

Using a voltmeter or 12V test light, check both sides of the brake light fuse for voltage. A visual inspection isn't the proper fuse test. Sometimes rust accumulates on the fuse box contacts causing bad connections. If you have voltage on both sides of the fuse, disconnect the plug at the brake light switch and check for voltage on the orange wire. If no voltage is present, check the wire for breaks or disconnects. If voltage is present, jumper the orange wire to the white wire. If all circuits are working, you should have brake lights. If the brake lights now work, the switch is either bad or needs adjusting. If the brake lights don't work with the jumper installed, check for continuity of the white wire through the "half moon" turn signal harness connector.. If there is voltage on the turn signal switch side of that connector, you probably have a bad turn signal switch.

Appreciate all the responses. Turns out my wire that was supposed to have power was dead, so I jumped a new one from the fuse panel to the brake switch and all is right with the world!

That said, this wiring is a mess and I'm ripping it all out and replacing it with an all new wiring harness. Best to start over so there's no guess work and I can rest knowing it's done the right way.

The truck now is a mix of the original harness, and new random wiring over it.

[devildriver6]

Originally Posted by 4x4 k1500

Did you use a tester to make sure you have current on both sides of the brake
switch when pressure is applied to the brake system?? Just because your brake switch is new doesn't mean it's good. Turn signal and brake lights use the same bulb element

You nailed it. No power to the brake switch.
Appreciate the response!

[devildriver6]

Originally Posted by Peanut74

As stated above do a continuity check on the switch to make sure it's good. If the switch is good check the wires are good. Do that by checking each wire to see if you have continuity to ground.

Hope this helps narrow it down for you.

Thanks for the help!