Turn Signals All Blink

[DenverDave]

I have a 2004 Chevy Tahoe. I recently upgraded the headlights (with Halos), parking lamps, and tails to aftermarket versions and converted the bulbs to LED. I added the Novita LM487 Flasher to get rid of the hyperflash. Everything worked great. 

 

I then had a new Kenwood Headunit installed (Excelon DNX996) and replaced the engine with a new 6.0. 

 

I say all of this because somewhere between the head unit and engine, unless I have my parking, fogs, or headlights on, All of the accessory lights (outside only) blink unless I have the fog, parking, or headlights on. I have replaced the headlight and foglight switch, installed a new LM487, and checked the wiring to the lights. Same issue persists. 

 

Wondering what it could be? I was thinking there may be a loose ground somewhere from the stereo install causing the blinkers to work correctly only when the lights have power? OR I am thinking it could be a bad Multi-Purpose relay in the fuse box. 

 

Any ideas on what it could be or what else could be going on?

 

Thank you. 

[Teach]

Replace all light bulbs back to OEM and willing to bet your problem will be cured.

[Jsdirt]

More than likely there's a ground that didn't get reconnected during the engine, or lighting swap.