S10 blazer electrical problem

1991 S10 blazer tahoe, 4.3 ,automatic,no a/c. the parking light/courtesy light fuse blows every time i turn on the parking lights. i have no dash or courtesy,license plate, or parking lights. all the other lights work fine {flashers, reverse,turn signals,} i even replaced the switch still blows fuse.no aftermarket lights are installed. any help would be appreciated.

So you have a trailier harness, there is a hot lead that is grounding out when the switch is on. Something is causing a short.

I checked, there is no trailer harness. everything on the truck is original except the radio. I thought it was shorting out and had hoped someone else had the same problem and could narrow it down for me. i guess i'll have to go wire by wire in the harness. thanx.

View msg # 88.