[radibob]

So the right headlight won't work when just the headlights are on BUT with High beams both right side lights light up ( high and low). New bulb and all new fuses.

Where is the ground for this right side headlight? and what does it connect to?

Am I right to be checking the ground if it lights up with the high beams?

Any other thoughts?

 

[86spider]

which year and model?

 

[radibob]

weird wiring issue

Oh sorry 84 GTV6

 

[al_cam]

On the 1983 The headlight grounds all go to a common point down under the ignition module or HT coil. bunch of black wires all going to single eyelet. One of those welded to the body nuts. The positive supplies all come from the air cleaner side, go across the front and the earths continue back into the engine bay on the opposite side.
Though from your description, I doubt it's the earth, unless you've got a dual filament bulb in one of the lenses. More likely dodgy contacts in the switch itself that finally gets forced into action by the extra movement of turning on high beam. maybe squirt some spray contact cleaner in the switch mechanism.
Good Luck,
AL.

 

[Stravs]

also check where the wires from your switch attach to the rear of the fuse box.