Led taillight issues

[ccautoupholstery]

I order led taillights for my 67 from brothers along with their led flasher. Had no problems for a couple weeks at least, but today an old lady followed me into Home Depot to tell me I have no brake lights. Sure enough, I have turn signals and running lights but no break lights with the headlights off or on. I have verified power all tge way back so I'm assuming something went bad in the leds but I feel like it is weird that they both went out randomly. Has anyone else had this issue?

[gmc684x4]

Did you double check your brake light switch on the peddle works and in adjustment?

[ccautoupholstery]

Originally Posted by gmc684x4

Did you double check your brake light switch on the peddle works and in adjustment?

I checked with a test light and is working fine at the switch, and all the way back to the connection points going to the taillights

[sick472]

LEDs do not draw near as much current which means the connections and grounds have to be very clean and neat.

Check and make sure the brake light buckets are grounded to the bed and then to the frame. If that checks out... Bench test your LEDs.

[ccautoupholstery]

After some more checking today at the connector before going thru the firewall...my brake switch is working and operating the wire for the 3rd brake (which I dont have) but nothing for left or right brake. My turn signals work fine and my running lights work fine. Makes no sense to me....oh also it does have American Autowire harness front to back and have had no issues in 4 yrs until now.

[Richard]

If you still have the original taillights swap them out. That will at least point you in a direction.

[ccautoupholstery]

Originally Posted by Richard

If you still have the original taillights swap them out. That will at least point you in a direction.

I am going to grab some bulbs to throw in, but I'm not getting anything at the turn/brake wires on the cab connector when brake is applied so I feel like I have something else going on

[Steeveedee]

If your turn signals and tail lights work, you have a good enough ground.

Go look at the cab wiring diagram. The turn signals for the rear use a different wire from the front so that the rears get the interrupt the brakes when the flasher operates.

With the turn signal switch in the neutral position, key off, step on the brake pedal (if you have power out of the stop light switch- you can check that by testing for power at the turn signal switch at the white wire from the stop light switch) and check the dark green and yellow wires. Now, turn the key on, and put the switch in one position or the other. Left turn is yellow, right turn is dark green. If you get pulsing power, then the turn signals work. If you got no power on those wires in the neutral position, the turn signal switch is bad.

Maybe VetteVet or other electrical expert can verify that I have this right.

[mr48chev]

I'm thinking I had that happen on my 71 and the 4 way switch was in on position but I didn't have a flasher in it. If memory serves right the 4 way bypasses the brake connection.

If you brake light switch is working and the turn signals flash the problem is in or at the turn signal switch because brake lights and turn lights use the same element on the bulb unless someone has done some changing.

[Steeveedee]

Originally Posted by mr48chev

I'm thinking I had that happen on my 71 and the 4 way switch was in on position but I didn't have a flasher in it. If memory serves right the 4 way bypasses the brake connection.

If you brake light switch is working and the turn signals flash the problem is in or at the turn signal switch because brake lights and turn lights use the same element on the bulb unless someone has done some changing.

Now there is something I've never heard of. Kind of makes sense, and it's easy to check.

[crewadmin]

Check your flashers

[ccautoupholstery]

It ended up being my turn signal switch. Thanks guys

[Steeveedee]

Originally Posted by ccautoupholstery

It ended up being my turn signal switch. Thanks guys

I'd like to know if my description of the trouble-shooting process helped. I'll keep it in mind for the next time someone has this question, and if I was wrong, tell it here, so that people aren't misled. Thanks!

[mr48chev]

Folks remember that the brake light wiring goes to and through the turn signal switch on these trucks as they only have the stop/turn / tail bulb with stop and turn being on the same element plus the back up light bulb separate.
if you have power from the brake light switch to the turn signal switch and not out when you hit the brakes it is the turn signal switch at fault When the turn lights still work. .

[ccautoupholstery]

Originally Posted by mr48chev

Folks remember that the brake light wiring goes to and through the turn signal switch on these trucks as they only have the stop/turn / tail bulb with stop and turn being on the same element plus the back up light bulb separate.
if you have power from the brake light switch to the turn signal switch and not out when you hit the brakes it is the turn signal switch at fault When the turn lights still work. .

Thanks again for your help!

[mr48chev]

No problem. Having three GM Trucks, 48, 71 GMC and 77 Chevy Dualie help me keep up on stuff.

[waters5]

Im stumped, Have autowire harness and dakota digital setup but no brake lights when engine is running and headlights on .

Headlights off: all turn signals and brake lights work

Headlights on with ignition off: all turn signals and brake lights work, taillights go from low light to bright red when brakes are applied

Headlights on with ignition on: all turn signal work, brake light dont change brightness. They stay super bright like the brake is applied.

[HO455]

From 600 miles away I'd say that your brake/taillight housings are not grounded properly. To verify run a wire from a good ground and touch it to the exposed part of the brass on the bulb while it is in the socket. The light should start acting correctly when it is grounded. You can do the same with a test light also.

To fix the ground at the housings do a search as this is a common problem. Both on restored and unrestored trucks.

[dmjlambert]

It could be over voltage, as in regulator not working. Super bright just because engine is running sounds like something to correct. To check it, test the voltage at the battery with engine running. Should be 13.4 to 14.7 volts.