LED tail lights

Reply Subscribe

Thread Tools

Search this Thread

Jul 16, 2025 | 01:10 PM

#21

Bikespace

Race Director

Joined: Mar 2017

Posts: 11,949

Likes: 4,507

From: Virginia

Quote:

Originally Posted by JC Pilcher

Lights- stock turn signal bulbs. Rear has LED tail lights. Side markers went back to stock bulbs. Installed the turn signals grounded relay on both hazard and turn signal locations. Hazards work as well as the running lights and the brake lights. When I activate the turn signal switch I get nothing. Dash doesn’t light up and neither do the tail lights. Looks like the fuses are good but I’m going to replace all the fuses with new ones. I checked to see if I have power to the relay and I do.

So by "dash doesn't light up", you mean you don't see green arrows when using the turn signals? Do the gauges light up (headlights on) and function otherwise? High beam indicator? "BRAKE" indicator?

I didn't see it in this summary. Have you tried the reversing base on the turn signal flasher with the current configuration?

You shouldn't need to replace any fuses, but I'm otherwise at a lost to explain what is going on.

Jul 16, 2025 | 01:26 PM

#22

JC Pilcher

Thread Starter

Intermediate

Joined: Dec 2023

Posts: 39

Likes: 6

From: San Antonio Texas

Yes all indicators on the dash work. Everything works on the car except the signals. I’ve tried reverse polarity and regular.

Jul 16, 2025 | 01:31 PM

#23

Bikespace

Race Director

Joined: Mar 2017

Posts: 11,949

Likes: 4,507

From: Virginia

Quote:

Originally Posted by JC Pilcher

Yes all indicators on the dash work. Everything works on the car except the signals. I’ve tried reverse polarity and regular.

Are there any LEDs in the turn signal indicators? It shouldn't matter in 70, since the bulbs are directional (you can get it backwards in 78-82).

I'm assuming you didn't try swapping back to stock taillights because you needed to cut and splice the wiring harness. Any chance the problem is there? A photo or three might really help. I'm really at a loss to explain what is happening.

Perhaps check the steering column connector.

Jul 16, 2025 | 01:50 PM

#24

JC Pilcher

Thread Starter

Intermediate

Joined: Dec 2023

Posts: 39

Likes: 6

From: San Antonio Texas

I’m at work at the moment so no photos. Yes I spliced into the harness and double checked the wiring on a schematic. I’m going to check the column harness I guess. It’s new as well. When I got the car the stock lights were shot.

Jul 16, 2025 | 01:58 PM

#25

walleyfisher

Race Director

Joined: Jun 2020

Posts: 10,685

Likes: 2,250

From: north of Chicago

2025 C2 of the Year ('64-'66) Finalist - Unmodified

2025 C3 of the Year Finalist - Modified

2025 C4 of the Year Finalist - Modified

2024 C4 of the Year Finalist - Modified

2023 C2 of the Year Finalist - Unmodified

2023 C4 of the Year Finalist- Modified

2022 C4 of the Year Finalist - Modified

2022 C3 of the Year Finalist - Modified

2021 C7 of the Year Winner -- Modified

2020 C4 of the Year Finalist - Modified

On my '74,
1. I have all incandescent bulbs in the dash
2. LED headlights (octain)
3. LED side marker lights (both front and back)
4. LED taillights/ brake light bulbs with the built in resistor
5. LED back up lights
6. Incandescent license plate bulbs (just haven't changed them yet)
7. LED switchback bulbs in front turn signals (white driving lights / w Amber flash)
8. The electronic flasher with the ground wire for turn signals
9. The electronic flasher with the ground wire with reverse polarity base for the hazard lights
Everything works great

Jul 17, 2025 | 03:47 PM

#26

60 SHARK

Melting Slicks

Joined: Aug 2016

Posts: 2,346

Likes: 1,174

From: CLEVELAND STUCK IN OHIO

2024 C3 of the Year Finalist- Modified

I've been through this with several older cars. One more check,,, apply brakes. If they illuminate, keep them on and apply a turn signal, (right or left) if the brake light stays on for the side you chose, you have issues in the column switch 😉...

Jul 18, 2025 | 07:40 AM

#27

augiedoggy

Le Mans Master

Joined: May 2007

Posts: 5,025

Likes: 1,120

From: North tonawanda NY

Quote:

Originally Posted by Eliredandblack

On my FIERO I installed LEDs in the tail lights. To get them working, I just purchased resistor units from Superbright LEDs. The only downside was finding a place to install the resistors. I still could use LEDs in the front turn signal without problems, so I just left the incandescents in.

Yes I was going to mention some times you need a ballast load resistor (which BTW negates the efficiency of the leds altogether and makes the leds less appealing to me for vehicle lights because of it) I had to install these in my truck when converting to led lighting.

Jul 18, 2025 | 08:17 AM

#28

Bikespace

Race Director

Joined: Mar 2017

Posts: 11,949

Likes: 4,507

From: Virginia

Quote:

Originally Posted by augiedoggy

You only need the ballast resistor if you don't use the 3-wire LED flashers (which the OP is using). I don't know about your truck, but it should be a simple plug and play for a C3 (front side marker lights are less simple, but still don't require resistors).

If not the steering column connector, my next guess is the turn signal switch (but both sides? odd).

OP, a wire-piercing test probe, like the one linked, might help you trace power more easily in the wiring harness, to narrow down where the issue might be.