weird light problems '92 Blazer

My Blazer has the demons. '92 s10, 4.3l, 4wd.

If the head lights are off and the truck isn't running the left signal works fine, the right signal works AND flases the dash.

Head lights on, truck not running, the left signal is fine, the right one dims the running lights, but no flash.

The hazard lights work as long as the headlights are off. If they're on there's nothing.

I pulled all the fuses to check them, they're all good and tight. I can only find one flasher and it seems good. I tried replacing the light switch, no change. The thing runs fine and all that. I'd check the grounds if I could find them, had a guy working on my other blazer and he lost my manual.

Any ideas?
Thanks!

It is time to start checking the ground wires and connections. This problem is very common. I think that you will find that most times, it has nothing to do with the headlights. It is the running/parking lights that share the common ground with the turn signal. The only time a headlight makes a difference is if there is a parking light that turns off when the switch is turned from parking to headlights, or the headlight shares the same grounding wire/connection.

If there is a trailer 4 to 3 wire adaptor it could also be the problem. I have only seen this two or three times in the last 30 years.......... a dual filiment bulb with an open, internal ground. So try swapping the left to the right side parking turn bulbs and see if it works (although it probebly wont)

remember opens make things not work, shorts make fuses blow

It sounds like its a ground wire issue as the previous person stated above. When you turn your headlights on, you put more of a load on the common ground. I would find the ground wire at one of your headlights as the common wire and ground it to the frame by just touching it and see if does the trick. I had it happen on my 88 trans am and it was the common wire. It sucked as it was dark out too at the moment
Conrad

Thanks fellas,
That's where my searching ancient posts was leading me, too. I've been looking for the common ground wire......I don't see anything. Mebbe I'll give THAT a search!

Thanks again,
Dan

Fixed!

Someone put a single filament bulb in where a double was supposed to be on the rear right turn signal, corrected that and the demons are exorcised!

Thanks for the help!

Dan