Stuck with low speed fan only

[79kcrew]

I’ve been chasing the issue of only having the low on my 79 crew for a while. I’ve put in 3 different relays (a used one and two new ones, I did jump the purple to the red and got high speed but it was constant even with the key off), a resistor, a blower motor, and a fan speed switch (the lever was broken off). It’s an A/C truck but the A/C wiring for the evaporator control switch is no longer there. Would that have anything to do with it? I’ve also cleaned the ground for the relay and blower motor.

 

[Jgonick]

Stuck with low speed fan only- you mean it only runs in the lowest setting- or it won't go into highest?

If you mean it won't run in highest setting-
Since you made sure the black wire on the relay is grounded good.
Next-
Check the orange wire running from the blower switch to the relay. When blower switch is set to high-The orange wire sends current to the relay to activate the relay -allowing the red wire to provide current to the purple.


IF you mean it only runs in the lowest setting-
Check the brn/wht wire running from the selector switch to the blower switch. FYI The brn/wht wire supplies current to allow speeds medium1, medium2 (by bypassing resistors) & high speed (org wire to activate relay)

Edited to add more info--