Need help with tail lights

[Sonny]

I purchased a rear light harness for my 1970 Belvedere a few months ago from year one. All four tail light sockets are junk, they’ve all broken, the sockets broke, bulbs do not make proper contact, etc. I bought four new sockets to splice in but trying to get the wiring configuration right. Now I am blowing fuses right and left and turn signals aren’t working. Could someone please tell me how the rear lights are supposed to work. 1. what do they look like with the headlights on? Are all 4 lights on and same brightness? 2. What do they look like when brakes are applied? Are all 4 on and brighter? And 3. What happens when the turn signals are on? The lights have never worked correctly since I bought the car therefore I don’t not know what they’re supposed to look like. I replaced all the fuses . I also replaced all the harnesses and the dash circuitboard last year. I just need to know How the tail lights function so I can get the wiring of the sockets correct at the rear. Frustrating.

 

[HawkRod]

I am surprised the Year-One harness was problematic. I used those for my restoration, and many others have used them as well with success. I have found them to be great harnesses that fit and function very well.

If you are blowing fuses you have something seriously wrong. Seems like you have connected power to ground somehow. You need to fix this first, likely by "undoing" your attempted fixes...

All four tail lights use 1157 bulbs and function the same way. These bulbs have two filaments in them: one bright and one dim. So for EACH of the 4 bulb sockets you need to deal with three things: Power from the running lights that gets connected to the dim filament, power for the brake and turn signal that gets connected to the bright filament, and ground, which goes through the metal bulb socket. Ground is not a separate wire, it comes through the car body and the housing to the bulb socket. However, while testing, connect a wire with alligator clips to a good ground source to be sure. One of the most common issues for lights not working well are bad grounds.

To answer your questions specifically:
1. what do they look like with the headlights on? Are all 4 lights on and same brightness? With headlight OR running/parking lights on, all 4 lights should be on dim

2. What do they look like when brakes are applied? Are all 4 on and brighter? Yes

And 3. What happens when the turn signals are on? The bright lights blink, regardless of the dim lights being on or off.

Do this:
a) Put a bulb in a new socket that I assume is disconnected from the harness (you said you bought new ones). Hook an alligator clip to the battery (-) and to the metal bulb socket itself. Then hook another alligator clip to one of the two wires. Then touch that to the Battery (+). Repeat for the other wire. You will now know which wire is the bright vs. dim.

b) Now at the back of the car, take the metal socket and hook that to a good clean piece of metal with an alligator clip. Protect the bare harness wires from shorting and turn the running lights on. Now take the dim wire you identified and touch that to the wires until it lights. You have now identified which wire to hook the dim part of the bulbs to. This wire feeds all four bulbs.

c) The other wires feeds the bright for brake and turn signals. On my 70, green is for left and brown for right. To find the correct wires, turn the lights OFF but the ignition on, and put the left turn signals on, Try as in step b above to find the wire that makes a light blink. This will feed the left two bright bulbs. Then confirm for the final wire for the two right hand brake and turn signals.

I hope this explanation helps...

Hawk

 

[Sonny]

I am surprised the Year-One harness was problematic. I used those for my restoration, and many others have used them as well with success. I have found them to be great harnesses that fit and function very well.

If you are blowing fuses you have something seriously wrong. Seems like you have connected power to ground somehow. You need to fix this first, likely by "undoing" your attempted fixes...

All four tail lights use 1157 bulbs and function the same way. These bulbs have two filaments in them: one bright and one dim. So for EACH of the 4 bulb sockets you need to deal with three things: Power from the running lights that gets connected to the dim filament, power for the brake and turn signal that gets connected to the bright filament, and ground, which goes through the metal bulb socket. Ground is not a separate wire, it comes through the car body and the housing to the bulb socket. However, while testing, connect a wire with alligator clips to a good ground source to be sure. One of the most common issues for lights not working well are bad grounds.

To answer your questions specifically:
1. what do they look like with the headlights on? Are all 4 lights on and same brightness? With headlight OR running/parking lights on, all 4 lights should be on dim

2. What do they look like when brakes are applied? Are all 4 on and brighter? Yes

And 3. What happens when the turn signals are on? The bright lights blink, regardless of the dim lights being on or off.

Do this:
a) Put a bulb in a new socket that I assume is disconnected from the harness (you said you bought new ones). Hook an alligator clip to the battery (-) and to the metal bulb socket itself. Then hook another alligator clip to one of the two wires. Then touch that to the Battery (+). Repeat for the other wire. You will now know which wire is the bright vs. dim.

b) Now at the back of the car, take the metal socket and hook that to a good clean piece of metal with an alligator clip. Protect the bare harness wires from shorting and turn the running lights on. Now take the dim wire you identified and touch that to the wires until it lights. You have now identified which wire to hook the dim part of the bulbs to. This wire feeds all four bulbs.

c) The other wires feeds the bright for brake and turn signals. On my 70, green is for left and brown for right. To find the correct wires, turn the lights OFF but the ignition on, and put the left turn signals on, Try as in step b above to find the wire that makes a light blink. This will feed the left two bright bulbs. Then confirm for the final wire for the two right hand brake and turn signals.

I hope this explanation helps...

Hawk

Thanks Hawk.
After some trial and error, I have the following:
-All 4 bulbs are dim with lights on as designed.
-all 4 lights are on bright with brakes applied.
-all lights flash with hazard flashers on
- but no turn signals at all. Replaced both turn and hazard light blinker pots as well.
Wonder if something in the turn signal switch melted when the fuses blew. The dash lights, dome/flasher, and tail light fuses all blew at some point. All fuses are good now.
Sonny

 

[HawkRod]

Thanks Hawk.
After some trial and error, I have the following:
-All 4 bulbs are dim with lights on as designed.
-all 4 lights are on bright with brakes applied.
-all lights flash with hazard flashers on
- but no turn signals at all. Replaced both turn and hazard light blinker pots as well.
Wonder if something in the turn signal switch melted when the fuses blew. The dash lights, dome/flasher, and tail light fuses all blew at some point. All fuses are good now.
Sonny

Hi Sonny,

Looks like you are making progress. The rear (bright) lights come on due to to brakes, turn signals OR hazard lights. If they work for even one of those things, then the issue with the others is under you dash or in the turn signal wiring. So your problem is now NOT with the rear harness. That is good and working like it should. You have some issue with the turn signals, and I agree the most likely place to start to look is your turn signal switch.

Good luck and let us know what you find...

 

[Sonny]

So apparently the new aftermarket turn signal switch wasn’t working correctly. I put the old dirty original back in. The lights have never worked so good! Thanks for the help!!