Great question. I put incandescents in the rear turn signals and all works as it should with the headlights on and off. I replaced the rears with LED and tried the same on the front with incandescents. Same result. I left one incandescent in on the left front turn signal with LED in the right front turn signal. The left side with the one incandescent works with headlights on and off, but the right side has the same problem.
Worst case, I can leave incandescents in the front turn signals. My goal was to brighten up the rear lights as they were pretty dim. Looks great with LED. That said, I’m hoping to track down this problem and go all LED.
Read the reviews on that flasher.
Several people have reported problems with that particular flasher when using LEDs. (on Amazon)
Sorry if I led you astray with that. I read the description and it seemed like it should be the correct one.
Someone else needs to chime in to find what actually worked with a full set of LED lights.
I've only done the interior ones myself.
Good news. The LED lights are all working. I installed the load resistors on the front turn signals and that did the trick. For a 1980 Camaro, the three wires to the front turn signals are Green, Brown and Black. The load resistors are connected to the Green and Black...the two outside wires of the three.
In the process, I did replace both flashers with an electronic flasher noted above and put non-polarity LED’s in. I put LED headlights in and all external signals are LED except the front yellow side lights. The LED was too bright there. The rear corner side lights are ok LED. The key I think is merely the load resistors and I only needed to put those on the front turn signals. I hope this helps the next individual searching for answers.
The dash LED’s are on my list to do soon. Thank you for you guidance and help. Much appreciated.