1986 Other Oldsmobile Models Cutlass 442 blower not working

Electrical problem
1986 Other Oldsmobile Models V8 Two Wheel Drive Automatic 91k miles

I have a problem with the a/c and heat blower not working on the high position. I replaced the high speed relay under hood and checked the resistor in the evaporator container. I also swapped the selector in the dash with another one and still no high speed. I'm thinking its wiring but not sure. It's hard to troubleshoot because you can't leave the selector plugged in and access the wiring to check voltage. Any suggestions would be appreciated.