I am just finishing restoring a 1987 K5 Blazer, it is stock except for an LS swap. I had to replace the wires for my dome light, it was working correctly off when the doors are closed on when open, on when I turned the headlight switch. Door switches are new, the last time I was working on it I noticed the dome light is on when the doors are closed (courtesy light is off as it should be) when I open the a doors the dome lights shuts off (courtesy light comes on as it should). Not sure if I have a short somewhere but everything else seems to be working fine. any suggestions or ideas would be appreciated

 

I figured it out on the weekend loose door switch on passenger side.

 

Thanks for posting an update. It might help somebody else in the future.

Glad you got it figured out.