electrical problem

my friend has a 89 s-10 extended cab with a 4.3. The problem is that the drivers front side marker doesn't come on when the headlights are turned on and flashes when you signal to that side. the indicator in the instument cluster flashes when signaling but, is always on when the headlights are on. any ideas???

Change the bulb.

I believe it is a dual filament bulb. One of th filaments is burnt out but the other still remains.

tried that already. sorry for not having that in my post.

You sure you used the right bulb?

yes. i looked it up in the book at the parts store and it was the same bulb as the one that was in the truck.

hey you might look at the bulb its only ment go in one way but if the socket is warn you can put it in backwards and only one side will get conection or it could be a ground problem