Thread: '51 Chevy taillight wiring

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I just got the brake light circuit fixed ( installed pressure switch instead of old mech switch ). Rewired the front parking lights/ turn signals and they are working fine, but I got a tail/ stop light out now. I thought it would be a good idea to rewire the tails anyway. So I got the diagrams out. Now the fun part comes, because the turn signals are dealer installed using a self canceling Guide 6004 switch. So the main diagram to the car does not include the turn switch, and all the taillight wiring goes thru the switch in 1 way or another.. I have the diagram to the turn signal system but it only covers that system and shows 1 wire going to the tails, when I know there are 2 as per the other diagram and my eyes tell me so.. What makes it worse is ALL the tracers are the same for brake/ stop and they all run down the drivers frame rail

What filaments are supposed to do what? I'v got turn signals on the left and right, parking lights on front and the right rear, stop lights on the right rear.. I can pass inspection with 1 brake light, but I want it right, at least for this year.. For next year, I think I'll rewire it all, and just buy a few miles of various colors and make it up myself. It's only got like 3 fuses, tho I'd probably add an easilly accessable fuse for every circuit with a rewire.. Orig look cloth coated poly harness is $500 for the main harness and $50-100 for the add on harnesses. In my case, I would need the main harness ( $500 ), powerglide harness ( reverse light, and NSS wiring, $100 ), taillight harness ( $50 ) and I think the Horn harness is a seperate $50 harness too. I'm not that stuck on original looking wires.. Car is on the road, I'm just working the bugs out

Put power and ground to the bulb--the brighter filament is for stop and turn, the less bright is for tailights.

The running light is the easiest. It can be the same supply as the other side! It's only running the one small filament.

That's what I thought. I have somthing very odd going on then, cause the turns work, but not stop and tail-lights on the effected light. Very simple electrical system so it shouldn't be too hard, even if I don't have a complete diag to work with.

With a simple circuit tester, find out which 2 wires flash at the T.S. switch. one should go to the front and the other to the rear. If they are working at the switch then you know it won't work at the rear.

If it is working at the front, then you know you have a wire problem between the switch and the lamp.

Originally Posted by 34_40

The running light is the easiest. It can be the same supply as the other side! It's only running the one small filament.

So I can cross that over from the working side? This is what both tail and stop has listed as how the wiring goes in the big diagram, but being my car has signals, I know it's very different, but I have to peice those 2 diagrams togther to make sense of it.

Originally Posted by 34_40

With a simple circuit tester, find out which 2 wires flash at the T.S. switch. one should go to the front and the other to the rear. If they are working at the switch then you know it won't work at the rear.

If it is working at the front, then you know you have a wire problem between the switch and the lamp.

That's the problem. turn signals work front and rear. I have no tail lights or stop lights on the left rear. tail-lights did work before I put the new brake light switch in to get the brake lights working. It's not the right brake switch, it's a basic pressure switch as my local carquest lists the orig as NLA, and the pressure switch was on the shelf. I don't think the switch diffrence will matter. It's for a 12v system but it's just a switch.

I'm going to re wire the tail lights as far to the front of the car as I can anyway.

First make sure all four bulbs are 1157s. The shorter of the two filaments should be the heavier ones and they are the stop lights. Remember you only need three wires at the rear, one for tail lights/ license plate and one for left stop/turn signal and one for right stop/turn signal.

Bulbs are 1154's, as it's still 6v, and the manual calls for them.. I'v got reverse lights also, but that only makes 4 wires.. I also cleaned all the contacts with Some DEX contact cleaner.

Matt,
Check your grounds. Lots of the older cars used plug in sockets with the socket to hole friction fit to the body being the only ground. Over time rust & corrosion can build up in the groove on the socket, or on the sheet metal the socket plugs into. An easy test would to hook up a long jumper wire (small is OK) to your negative battery post, and then touch the other end to the light socket of the bulb not working to see if it lights. My old '60 Chevy (3 lights each side) used to get into some really funky blink patterns because of ground problems, and sneak circuits when it "hunted" for a missing ground.

You have to split the stop light wire coming off the switch at the master cylinder

I think I traced it to the light socket. I can get it to light by wiggiling the wire. The contact inside doesn't look healthy.. I ran new wires for the turn signals, 2 diffrent colors so I can tell them apart.

The ground is what I first thought of, and I manually touched the light socket with bulb to the trunk latch, and that's where I found by wiggling, it will light. The original wire for the tail light on that side looked not so great, so I tied it into the license plate light wire ( All shrink and solder, no butt connectors ). It has good power now. can't test the brake light power without a helper. If I can't get the brake light to light that side, I will tie it directly into the stop light switch. Right now, the switch is wired in the factory way, just the wires are extended to utilize the pressure switch.. But now I have to figure out where to find the

I have a couple 36" test leads that I will make longer to test the grounds further. I was going to buy Alligator clips and make my own but the pkg of 4 alligator clips was $2 and the 36" assembled test leads was $1.50.. The only complication I have now is finding a socket to fit. There the spring fit- click in style and I know I could add a basic dual filliment socket but I would loose the ability to remove the bulb without removing the backer plate. If it gets me out of a pinch it may be just what I do, as I have 1 on hand but only if I can't find the right thing. removing those 2 screws and getting them back is a PIA with how far the tail lights are stuffed into that corner under the trunk lid. Chevy didn't make it an easy car to work on in the sense of how/ where things are located, but it is very simple in how it functions.

Now noticing that the restoration suppliers are selling the same type of replacement socket as I have as sockets that fit '51-'52 Chevys, but There sockets have a neat little tab for a spade connector to connect for ground too. I'm going to try mine first, and if it works but has a sketch ground, I'll buy 2 of those sockets and run a 12ga ground wire right to a factory ground connection, and create seperate a ground for each socket back there, so that ground is not an issue. I could easilly just go right to the trunk floor with a self tapping screw, but the floor is in great shape w/ factory primer still and I'd rather not create a point of corrosion.

Wired, tails and turns are working but no stop on the left side, so I'm going to jumper in a connection to the stop light switch directly.

If you don't have a stop light working on the left side you also don't have a turn signal on that side either as it's the same element. On a car of that age you only need three wires to the rear, left stop/turn, right stop/turn, and tail lights/license plate.