Only 3 of 4 blower fan speeds?

[Gordonr1973]

Hi guys;

I'm trying to find a gremlin in my heater/blower fan system...the 2 lowest fan speed settings blow the same in my truck. When I switch to the 3rd and 4th, there is a definite difference.

I changed the fan motor, the relay and double-checked my wiring vs the wiring diagrams listed here on the site, everything looks fine.

The only thing I didn't pull out to inspect was the control switches in the dash...any suggestions??

[TrailerTrash]

it could be the switch itself. my 79 was kinda the same way. it worked on low and high only. the middle two settings werent any faster than the first. took the switch out and it was shot. just wore out from years of switching

[motornut]

some trucks have a blower fan thats "factory wired" always on, for venting.
the ones I've seen are jumper-ed at the switch.
removing that ,changes the lowest speed to off,
I've seen the coils for speed control fail and do that,are yours ok in there ?

[Gordonr1973]

Yes, coils are okay, no broken wires. I'm thinking I'm going to have to chase wires in the dash and replace the switch. I might do that tonight.

[Gordonr1973]

Update, I chased every wire, every connection from the switch to the relay. Nothing wrong.

Seemed to work perfectly in the garage, I took it for a spin today, as soon as I clicked on the AC so the compressor engaged --- zzzupp ---- fuse fried.

Unhooked the compressor and all seemed good, going to check to see what's up with it this week...