indicators not working

Hi
I have a problem with my indicators and hope someone can advise , if I have main beam on and I go to use indicator to turn right my indicator does not work(no noise from relay and slight dim coming from it), but if I only have side lights on the right indicator works.
The left works all the time.
Also noticed that the right hand(drivers side) front light(main) is alot dimmer than the other as if there is a voltage drop of some kind.
Tried new lights in the front and checked all bulbs all seems to be ok.
Anyone got any ideas
90 TD p/u

thanks

I suspect a bad earth. You need to check the grounding of each dodgy unit. Clean up to bright metal and vaseline for the future.

Definite earth problem. Happens all the time.

ok, thanks for the replies, I'm on the way out now (in the rain as no garage) to check all earths
thanks

ye,sorted
I can't believe a little earth screw failed my MOT
at least theres no retest fee
cheers lads/girls

Not sure about shifty, but I'm definitely male.

Me too !!!!!!!

I have the same thing. See, I used the 'search' function.
Side lights on, all lights work OK.
Dipped lights on, left indicator works, right one doesn't, indicator warning light on dimly. right headlight dim.
Main beam, as above but indicator warning light is slightly brighter.
OK, so it's the earth. Where should I be looking?