LED tail light signals will not flash when lights are on

[calgary72]

I installed LED plug and play tail lights from LMC and the signals will not flash when the lights are on. I installed an electronic flasher (with ground wire), also from LMC. I also installed new LED headlights (in case that makes a difference).

I understand that flasher issues are often related to bad grounds. After it didn't work the first time I relocated the flasher ground and took apart the taillight assemblies and sanded the contacts with the frame and cleaned and sanded the inside of the plugs. Still would not flash when lights are on. Light goes on, just does not flash. I re-installed the old bulbs and works fine.

Can anyone help? Thank-you for any suggestions. I searched the forum and couldn't find anyone who had the same problem.

[Steeveedee]

Not to be a wise guy, but did you put the electronic flasher in the turn signal socket or the flasher socket? When I put the LED assemblies like you have from LMC, I left the incandescent bulbs in the front, and don't need an electronic flasher.

I did notice that on mine, the right brake like comes all at once, and the left lights up one column at a time. I'm going to have to find out how to change that. They both used to light a column at a time. I hope that doesn't mean it's going bad.

[calgary72]

No problem. Dumb moves are a possibility for sure. However, I put the electronic flasher in the turn signal socket. Just in case, I moved it to the other socket (and switched the other flasher). When I did that, the lights didn’t even flash when the lights were off.

[dmjlambert]

Do the front turn signals flash when headlights are on?

[calgary72]

No, nothing flashes when the lights are on.

[dmjlambert]

What kind of bulbs do you have in the front turn signal/parking lamp?

[calgary72]

LED in the front part lights

[dmjlambert]

If you can make it blink by plugging and unplugging the flasher module, and everything else is OK, then I would blame the flasher module. I've heard of people installing LED bulb resistors, to simulate the load of a regular filament bulb. That could be a solution, and then you could use whatever flasher module you want. Steeveedee mentions above just leaving regular incandescent bulbs in the front parking lights, that may be an option too. I can't think of much advantage of LEDs in front. LEDs in back are advantageous because they give your brake lights instant on.

[dmjlambert]

And by the way, this problem you describe is indeed very weird. You would think turn signals are not impacted at all by headlights being on. They are a different circuit. The only thing that sort of puts them on the same circuit is if you have a ground problem, but you already check that.

[Richard]

Doubt it has anything to do with the headlights. The side marker lights are tied into park/turn circuit. When headlight switch is pulled out to park light position is the condition the same? Maybe nothing to with it but on the 72 and maybe 71 the front markers alternate with the turn signal. Think the marker is grounded on the lead to front turn. Hate to think this but I would bench test the led assembly's due to where they came from. Nothing worse than chasing problem that is derived from installing a defective part.

[VetteVet]

I remember a similar thread where one terminal of the flasher was not grounded in the fuse panel. I'll see if I can find it.
Do the LED lights light up at all?

[calgary72]

The leds flash when the lights are not on. I think I will take the suggestion of bench testing the lights. I'm not sure which was flashing, the brake (bright) light or the tail light. Could be that the unit is not wired properly. I won't be able to check for a week or so. I will post what I find out. Thanks for your help.

I get that the front signals do not have to be led. They do look slick though....

[dmjlambert]

Richard pointed out that the headlight circuit and turn signal circuit are connected by the side markers. I suggest disconnect or remove the bulbs from the front side markers and see if the behavior changes. If the problem is resolved then you can try some incandescent bulbs in that position.