So I was flagged down yesterday in my 1950 chevy on the way to a cruise night an told I had no brake lights. Well I had one brake light. My 3rd was working fine (1937 ford tail light used as a 3rd at the top center on my rear window) I got home and checked the bulbs, one had a broken filament so I ran to the auto store and bought a new pair. Changed them in hope that it was a looped circuit or something funny due to the broken one but still had none after swapping them both. I have turning signals, running lights and all grounds are good. I have power at both terminals of the brake switch when the pedal is pressed. The switch is mounted under the dash on the car. I have checked all the fuses and such. I even broke the connection at the switch so I would have had brake lights and wiggled wires checked connections in the rear and all and still nothing. It happened out of nowhere and I can not figure it out. Car uses a 1958 biscayne column and aftermarket ez wiring 21 circuit harness. I had read maybe a hazard switch but the column doesn't have one. My turn signals work perfect so I'm ruling that out too. The wiring is ran straight through clean with no splices or cuts. It has not worn or rubbed through anywhere that I can see either. The car does have a rough ride though which I guess could have worked something loose but I think covered just about all of it. Any help or ideas?
The same wires that provide power to the turn signal filaments also power the brake lights. I would think there is a problem getting power from the brake light switch to the column. I just reread and you said that the third brake light is working...that would rule out what I said previously.
If you break it down, the brake light switch is OK from your testing, the lights and wires to the rear are OK since the signals work. That leaves either the wiring between the brake light switch and the turn signal switch or the turn signal switch itself as the possible troublemaker.
The 3rd brake light does not go through the turn signal switch. the others do. the turn signals work so wiring is ok. check the wire from the brake lighte switch to the turn signal switch if ok it's the turn signal switch.
Did you have all brake lights working before this ? Where did you tie in to get the third brake light to work. ? Most harness now have a dedicated third brake wire. If you had brake lights then tied into the wire to get the third to work you would have the third working as a turn signal for one side are the other. Turn and stop are the same wire at the tail light. Possible to have the little card in the tail light housing a turn to one side so the bulb and the wire are not making contact ? The junk bulbs we get now sometimes don't make good contact.
Since your third brake light works you can assume your brake light circuit is good at least through the brake switch. Are you using operating the taillights through an original type turn signal switch in your Chevy column? If so it sounds like it could be a switch problem (or loose wire to the switch) as both the brake light and turn signal circuts to the rear taillights run through the turn signal switch. Your taillight bulbs have two filaments, one a running light, and the other brake/turn. When you activate the turn signal the switch "breaks" the brake light connection to the selected taillight so the light will still flash when the brakes are applied. So check the brake light circuit to the turn signal switch and if that is good check the switch itself.
Sounds like you have eliminated all possibles but two. How is the third brake light isolated from the turn curcuit? If the problem is not in the isolater then you have a bad turn signal switch. Even when both turn signals work perfectly the switch can, and often does, kill the brake lights. I have noticed that seems to be more of a problem when the switch carries additional load, like a trailer or third brake light.
I recently had the exact same problem with my 1953 International, but I have an aftermarket turn signal switch. It was driving me crazy because everything checked out. Turned out there was some tarnish on the contacts in the switch so that it wouldn't allow continuity from brakes. Wire brushed contacts and it was good to go.
The turn signal switch was replaced with a new original one a couple years ago by the previous owner, brake lights have always worked in the car without issues up until what seems to be within a couple days or as of just yesterday. I guess I will have to pull the wheel off to access the turn signal internals and see what's going on? I'm not sure about the brake wiring routing, one of the wires running to the brake switch does say "third brake" on it andhas a 2nd wire tied into it but unsure of what it is or its routing. Not sure where the other from the 2nd terminal is running to either. I did not see any rear brake writing on the wires running to it but the wiring to the tail lights say "turn signal" & "tail lamp" I am not near the car currently nor for the next few good hours (stuck at work) but will start looking into turn signal areas on the column. There is a junction block looking unit down on the column near the frewall where a few wires run down the column to but the wiring on them states turn signals front/rears if I remember reading correctly. It was dark out when I really stated digging in. Thanks for fast replies.
If you have two wires from the brake switch then one goes to 3rd brake light, the other to the turn signal switch.
Do you have dash lights? The dash lights and tail lights used the same fuse in the factory wiring. You are using an after market harness and it may be different.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Rich nailed it, as the third brake light most likely is connected in before the turn signal switch. Replaced a "couple of years ago" is still used as far as electrical components go. But first I would check the connection between the brake light switch and the turn signal switch as it seems really odd that both brake lights would go out at the same time on a turn signal switch.
Ok, I did pull the wheel and checked out all of the internals in the column, that was all like brand spanking new in there. It was what was all replaced when the column was put in (turning components, rods, contacts in the column). The junction/module at the low section of the column near the firewall was bad, the set screw mount that holds the cable from the turning switch was cracked and no longer held the outer sleeve in place. Also looks to have burned a hole in the side of case from heat. I took it apart and the contact from the brake switch terminal has melted and was cocked sideways and was not making contact also had a few small pieces of plastic fall out of it that held the terminal points in the tracks. I pulled the brake switch wire, left turn and right turn and "Y'ed" it off from the brake switch wire to the turn wires, I now have brake lights but bypassed the turning signal. So I can still drive the car while I attempt to locate a new switch, any good leads for a good quality unit? Thanks for all the replies! Here is the culprit:
Early 60's GM ? They now repo those. Mark your wiring. Mass confusion for old guys.......................