I have a no turn signal on a 65 Chevy C10. Out of the blue I lost taillights. Knew I had bulb socket and wiring problems at the lights. I replaced headlight switch, flasher and new tail lamp housings and new tail lamp harness with the correct connectors for bulb sockets and rubber connector to the cab harness. Correct GM color code yellow left green right. Had running lights and brake lights no turn signals. It has a late model GM tilt column for automatic trans. I'm ***uming it is 67-72 by the looks of the switch. The switch itself is black with D-8-67 if that is a clue. The old switches have two c shaped connecters a 3 wire and 4 wire. These were spliced onto the late model switch with wire color match to cab harness. I checked this at the cab harness. Key off (no power to purple wire from flasher). A hot wire from battery to each light terminal and each worked for color code match. After removing tape to check the old splice I noticed a brown wire cut off. I later learned the brown wire is the power wire from flasher to the hazard circuit on switch. A 65 truck did not come with a hazard flash, so they just cut it off. I installed the new switch and connectors same problem. On the late model switch when you engage the flasher ****on it connects all wires and gets the constant power from the brown wire at flasher to work with ignition off and disconnects the purple hot wire for turn signals from flasher. To check. I engaged hazard ****on, key off and connected jumper from battery to brown wire and all lights worked (bright). Next with key on (power to purple wire from flasher), flasher engaged nothing. This proves the hazard ****on engaged does cut power at purple wire in switch. Now comes the confusing part. No blown fuses. With key on (Power to purple wire at fuse panel flasher). If I engage turn signal switch left, I get both taillights and left front turn signal flashing. Same way with right. If the switch only connects left or right side not both. The taillights are connected together somehow. The next test I did was with switch harness disconnected. With key on I ran a jumper wire from the purple wire tab to each front wire tab (blue & lt. blue) each light flashed separate. Front lights are turn signal only and are not wired to headlight switch circuit only turn signal circuit. If I jump purple wire to yellow (left rear) tab or green (right rear) tab both lights flash. This tells me it is not the switch, as well as the second new switch I tested, and re-tested old switch. I read on Painless Wiring site there is two options on flashers working when engaging switch. One is if the hazard ****on is not dis-engaged even slightly the turn signals will flash. Second is if any one light socket has the two wires crossed it will cause all the lights to be connected from the headlight switch. I did test this with the headlight switch harness connected and dis-connected. Taillight bulbs (staggard pins) can only twist in one way. The only other possibility is the twist on connector on the taillight harness. Don't remember if it will connect either way to cause the wires to be crossed. I have to check. Sorry this is so long and confusing, but I hope someone has some ideas with all the info.
Rockit; I have a 66 shorty myself and recently converted to all led signal lights.. I found that the factory lights were/are grounded to the sheetmetal of the hood. Wouldn't work without that connection. Taillights were ordinary but the ground I spliced into went to screw in frame just below taillight housing. Don't know if that helped or not but mine are working fine. Jer
My front lights are grounded I guess from the screws into the hood. They do work so I ***ume they are getting ground. My taillights both have a separate ground wire from housing to frame. I disconnected my taillight harness and tried the front lights. They each work left or right. Seems only the taillights are all connected somehow. Strange because everything worked before. Might be a short in the harness or wires connected at the flasher in the fuse panel. I hate to think about a re-wire job.
Make sure that the taillight ***emblies have a good ground. If the ground is bad then the turn signal flashing input to each taillight will seek a ground through the tail lamp filament and from front parking lights. An easy way to check the grounds is to use a wire from negative terminal of battery to the metal part of bulb socket. If light works properly, then you have bad grounds.
I'm having trouble following your trouble shooting procedure, probably my A.D.D. HaHa. What helps me in trying to diagnosis electrical problems, is to make a drawing of the wiring and follow it through testing with a VOM meter. Like others have stated most problems are grounds. Run a jumper to the lamp housings to a good ground and see if that lights the lamps. Did you by chance convert to LED lamps or still using incandescent?
Yup sounds like you need a better ground. I went threw a similar chase after getting a flat tire and thought I’d just broke the bulb. Turns out it had shattered the housing the light plugs into but it was holding together enough for me to swap the bulb once or twice with out noticing before it turned to crumbs! good luck
The housings each have a wire connector sandwiched between the housing and body at the mounting screws to the frame. I have to remove the housings to get at the bulb sockets to test. I had cleaned the connections earlier.
Stick or automatic? Recently chased a turn signal issue on my car. It was a random problem that would come and go. The newer ****ty connectors at the base of the column were separating when I was pushing the clutch in. Took a while to find it. Took the damn connector out and wired in individual connectors and no problems since. Just a thought.
By the way I want to thank everyone for responding with the help. As far as the ground wire. The housings have a chrome trim molding covering the housing. You have to run the screw through the molding and housing, slip wire eyelet over screw and hope it doesn't fall off when guiding the rubber boot and housing to body. Might be better to just wrap the wire around the screw then a thin washer to guarantee the connection?
I suspect you have a ground problem at the rear lights. Try turning on the left turn signal with the key on. Previously you said you get the left front light and both tail lights. Now, remove the right tail light bulb. If it is a ground problem, both tail lights should go out. The reason for this phenomenon is that the tail lights have a mutual connection through the dual filaments. If they lose their ground the current tries to ground thought the other filament and running light wiring.
What you have there is a way to confuse yourself and the rest of us. What you need is a wiring diagram to follow from what your working on, that which your installing, and one that show's how it's to be done. Advice like that is priceless. I'm going to suggest you take it under advi*****t. Hell, I'd go so far as to say if you don't, you'll be searching grounds like it's the answer to all electrical problems. 1965 turn signal / brake light rewiring issue - The 1947 - Present Chevrolet & GMC Truck Message Board Network (67-72chevytrucks.com)
This truck has been sitting in garage several months. The problem occurred after sitting not any driving or wire changes. If the lighting worked before it was wired correct. First wire change was splicing in color correct 65 separate 3 wire and 4 wire connectors to new turn signal switch harness. Replaced headlight switch, flasher, both taillight housings, taillight harness and turn signal switch. At this point everything is wired as it was except confirming the ground connection at taillight housings. I'm checking the grounds next. As far as a wire diagram, which does show where and how everything should be connected is fine. But when someone like myself looks under dash at the maze of wires and wires all wrapped up in a harness running to where you can't even see is a little intimidating. I do have a 67 C10 to restore and I will learn more when I rewire it.
The turn signals to the front are wire separately from the rear ones because the rear lights also function as brake lights. To trouble shoot, I suggest checking the brake light function first. Do they work?
Brake lights work. I did the test for ground with bulbs. Key on left signal on, removed right bulb left bulb stays on. Same thing with right as well. ***uming there is not a ground problem. With key on the purple wire gets power at the flasher to the harness to signal switch. The signal switch connects either left or right. I would think at the harness from flasher if I connect a jumper wire from purple wire tab to either the left or right taillight wire tab only that light would flash. Either wire connects both lights.
Flick the turn signal lever for left turn without turning on the ignition switch. Step on the brakes. The right side bulb only should light up and vice versa for right turn.
The key to diagnosing electrical issues is to be methodical; start at one end or the other and work your way to the opposite end. Jumping around only leads to confusion. Verifying the switch is working properly can be critical, the procedure for that is here... Turn Signal Wiring How-to | The H.A.M.B. (jalopyjournal.com) although that may not be needed. You should have at least 8 wires coming out of the column: three 'power in' wires consisting of the brake light power from the brake switch, turn power from the flasher, and emergency flasher power which in your case is unused, but would be from the emergency flasher if present. You'll have 4 output wires: left front turn, right front turn (and these may also supply the dash indicators if used), left rear turn/brake and right rear turn/brake. You should have at least one more wire, for the horn. And possibly one more, for a light at the shift indicator. I'll note that one thing I've learned is NOT to trust 'color codes' on wires. Yes, they're supposed to identify the wires but one mistake can drive you nuts. I'll physically verify that each wire goes where it supposed to. 20% of males have color blindness to one degree or another, and I've run into new parts with wrong color coding more than once. As the original problem was the taillights, I'd start at the rear and work forward. First I'll note that the taillights should have NO connection to the turns/brake lights other than sharing a ground. So remove the rear lamps, unplug the harness supplying them at the front and verify that there's NO continuity between the three wires which would be taillights and left/right brake/turns. If you find any, there's your problem. Disconnect the sockets from the wiring one at a time and check, if the problem goes away you have a bad socket. If that doesn't clear it, it's in the harness, you'll have to open it up to find the problem. If all that checks OK, look at the lamps. Read each lamp filament to ground and note the reading on each. Now read between the lamp contacts. You should see a value of more-or-less reading 1 + reading 2. If the reading is much lower, the lamp is defective. Good luck!
Before you get too carried away, Do you have a working flasher in the 4 way flasher socket? If you don't and the 4 way switch is pushed to on your turn signals won't work with some switches. I fought that one on my 71 GMC when I had the 4 way flasher out for some reason and then didn't have turn signals. Laying under the dash and looking up it finally registered.
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