I recently purchased a 1994 GMC Jimmy S15, four door with 241,000 miles. Last night I went ahead and replaced the Blower motor and Blower motor resistor. Now I have a weird issue. The purple power wire has 12 volts, when you start the truck everything works. As soon as you turn the truck off, and then turn it back on the Blower motor no longer works, but when you disconnect the power wire, then reconnect it everything works. I was wondering if anyone has ever had a similar issue?

 

What's the voltage on the purple wire when the blower motor is running and what is that voltage when it is not running? Where are you connecting the ground probe for the meter?

George