Weird utility trailer light problem (I know, not a mopar)

[DocMel]

Posting here because of good help history:

I have a simple and small utility trailer

All my trailer lights work fine  (four pin) : Brake, tail and running lights, all good to go

Now here is the prob:

Everything works ok, EXCEPT when the engine is running.  I know, it sounds crazy.

As long as the engine is NOT running, all the lights work ok

When the engine is running, the turn signals become very weak and work very erratically

[Chryco Psycho]

do you have a good ground on both , it may be using other circuits to ground & cannot ground when running ?

[pink panther]

maybe the flasher

[DocMel]

Grounds were the first thing I checked.  I have three grounds.  At the hitch, and at each taillight.   But what i did just in case was to retap each ground into the frame, just in case

Flasher is relativley new, but Ill switch out with a new one and see

[roadman5312]

  I have some ideas. Check voltage at fuse with key off, then key on.  I'm thinking maybe ignition switch. It has to have something to do with voltage in run mode vs off mode.    I love this kind of stuff.   

[Chryco Psycho]

You may need an HD flasher with the extra load