Brake light gremlin

[chevyhed53]

Having a frustrating time with this electrical issue on my '56 stepside: All my lights, front and rear, work fine with the exception of my right brake light. Left brake light is fine, and the right rear turn switch works fine, which is maddening. Went through the obvious--bulb, etc., and I'm mystified. There is power at the brake light switch under the dash. I have a keyed GM column with the smaller GM 3 7/8 connection. Any ideas?

[dsraven]

start at the light, it would help us to know what light housing you have-pic, remove bulb and look down into the holder. you should see the flat wire insulator with 2 wire contact nubs. make sure the insulator has not and cannot turn. if it does turn the bulb contacts the wrong nub or doesnt contact a nub at all. usually there is a slot that the insulator fits into.next take the test light and see if you have power on the nubs. use tape or hose to insulate the test probe so you dont short to ground on the bulb housing. put the test light ground somewhere good for grounding.try the tail, stop and turn seperately. if they all work try putting the test light ground on the bulb holder, that is a common issue to have a poor ground through the light bulb socket. you can also put the bulb back in, after all this, and test to see what is happening with the bulb elements on each circuit as you try each one seperately. you can also try a known good light fixture to see if that fixes the problemif all good keep following the wiring back to the switch. maybe got pinched somewhere. brake lights go through signal switch, have you checked signal switch output for brake power with signals in normal position but brakes applied?

[57chevyman]

do you have original style tail lights? i had issues getting everything to work with my tail lights. in my case, although the tail light bracket is supposed to be the ground, i had to run a separate wire for a stronger ground.

[chevyhed53]

Thanks very much for both responses. I have original-style housings, repro probably from Eckler's (can't remember, could be Brothers). I also had trouble with proper grounding when I first installed them, and had to add an extra ground wire. One quirk is that the insulator can be installed can be two ways--both of the tabs that lock it when you turn it are the same size. I'm thinking the problem is at the turn signal end, as I had not touched the housing and bulb until it stopped working. I'm forging ahead! Thanks again.

[dsraven]

if you get the light issue fixed, the insulator, then next you need to check for a brake output at the signal switch. you should have a power output from the brake switch that goes to an input on the signal switch. the brake and signals use the same bulb element. check at the switch to ensure that you have 2 hot wires, a left and a right, exiting the switch when you step on the brakes. if not it is likely the signal switch giving you grief or a wire from the switch is broken in the column somewhere.

[chevyhed53]

Have power in and out of the steering column connection (white wire) and power at the under-dash brake switch. Weird.

[dsraven]

not sure about colors etc in your column because don't know what it came from but, you probably have a fused, hot at all times, power source feeding the brake circuit. from there that wire should go to your signal switch. coming out of the signal switch will be 4 wires for signals, (possibly 6 because 2 could also go to the dash indicator bulbs depending on how it is wired). 2 wires go to the front lights and act as signals and 4 way flashers on the same wire. 2 wires go to the rear lights and act as signals, 4 way flashers and brake lights on the same wire. if you can find the wire that goes to the rear side light in question, and test that wire for power at the signal switch output, you can eliminate or fault the signal switch in one easy test. you can also power that wire with a jumper wire to continue testing for faults if the signal switch is good. physically touch the harness all the way to the light from the signal switch. tug the harness between 2 hands and feel for stretchy sections, that may indicate a broken wire, or for lumps that may indicate a junction/butt connector. I would say, without seeing the truck, that since the signals work but the brakes don't you have an intermittent fault in the signal switch that isn't letting brake light power through the switch when the switch is in the neutral position. could be just dirty contacts in the switch.

[_Ogre]

your right rear turn signal is also your right rear brake light: same wire, same filement in the bulb
if the turn signal works then the brake light works, unless the turn signal switch is bad or wired wrong

either signalstat or built in the column will wire the same as the top picture
your switch is bad

[mr48chev]

Ogre said it all right there. I have almost the same problem with the wife's Monte Carlo that I have to tackle Saturday. on it neither the brake light or left turn on the rear work though and I've done the change the bulb thing.

Since the left side works ok I don't think you have one of those columns off a rig that had separate stop and turn light circuits. You could check the stop light wiring to see if originally the wire had been tied into the left turn wire and there is no connection to the right turn wire. In that case you either need to change the switch out to one that runs the brake lights though the turn lights or install and wire up a pair of separate stop lights as tying them together to get both brake lights to work will cause both lights to flash when you hit either left or right turn.

[dsraven]

since you are using a keyed gm column, I assume the sigs and brakes are like a newer gm would have, same circuit-same bulb element. I mentioned to check the obvious bulb socket deal first just in case there was an issue there. personally, I think the switch is toast. do some quick testing on the switch output and see for sure, but I think a steering wheel pull is in your future

[chevyhed53]

Yep, pulled the steering wheel, replaced the switch, which was pretty beat up, and all's well. Thanks all for the help!

[dsraven]

that's awesome. great it worked out for you. fun getting that wiring down the column eh?

[chevyhed53]

Yeah, a real joy! A little cursing and swearing, but it's done!

[_Ogre]

A little cursing and swearing

your a better man than ogre, he cursed a swore a lot building truk