Head light switch problem, please help

I have a 1991 Mustang without fog lights. We have a wierd problem. The headlights work, but all the parking and taillights will not work at the same time. If we play with the headlight switch a little bit, and leave it in a position about 3/4 way on, all will work, unless you bump it.

I swapped out a new switch, and the exact same thing is happening. I heard a relay clicking on when the park lights would work, and I swapped it out as well with no new results.

Does anyone have an idea what is going on or where I should check?

Sorry if this is not in the right forumn, I did not see one that matched my question.

Fix to the headlight switch problem

Well color me stupid. The left headlight had literally exploded the glass, so we changed it out. But then the park lights would not work unless you fiddeled with the switch, I could get one set of the other to work. It was very strange.

Nonetheless, I found the issue. The headlight must have blown the 15 amp fuse for the park lights. The red herring was the oddball. Just by playing with the switch I could get them to work by playing with the switch.

End result is it is fixed.