Hey New to the forum,
having blower fan issues
1990 Chevy C1500 2D 2WD 4.3L
All the post I've seen about heater blower fan running High is when Only the high switch works. This is not this problem. The heater blower runs HIGH by default when turned on, low, med (same High speed) except when the switch is set on High, then it turns off. What?
I've replaced the resistor with a store bought(said it would fit this model, notice they were not exact, there was only two loops, where as the original has 4) also got an original from a donor car but it didn't help, same thing. Checked the one fuse under the driver side, looks good. If it was bad the temp controller display would be blank in that area. I've got 12v going to the blower purple wire, used the ground and made a ground connect didn't help. I've replaced the 3 relays with donors and one store bought. Swapped them around measured the voltage, the relays seem to be working. Would the relays cause this? Is there another fuse somewhere, could it be the control board switch itself? Thank You