when headlights are off indicator lights work fine. When headlights are on (day or driving) it also powers on the passenger side indicator lights front and rear, and quite bright. Also the indicator function does not work anymore for that side. So, somewhere they are getting quite some power.
Could this be from fuse box? Could this be from light switch?

Any help please.

 

that might not be the case. What is the difference between single element and multi??? element bulbs? My bulbs are single contact, so how can they be dual filament / multi element?

 

ForcedInduction,

you are completely right. I didn't check all the lights correctly. Many thanks, as I was getting desperate after checking every ground in the car.
Learned a lot about the wiring tho

Wes