If no high speed fan and/or no Heat try this!!

[67mater]

So, I'm cheap and working on two trucks (3 switches) that had no high speed, only low. I noticed upon removal of what I thought was a junk heater control box (broken knobs) that the switch looked corroded. I took the two screws out, and removed the switch (watch the bushing for the middle arm) and found I could not switch it easily by hand. So, soaked it in WD-40 and then played with it until it would switch through all 4 positions easily. I reinstalled and low and behold I get low speed just shy of all the way over (middle bar) and high fan all the way over (hold your breath it'll probably blow some leaves out at first)

For heat, I knew there was blockage in the outter heater box as the heat flap wouldn't close completely and there was never any air through the heater core section (I removed the 1st and 2nd section of the inner box as I didn't want to remove either inner or outer box at firewall due to ease of screw access and having to redue seals). I unbolted the pass. hood hinge at the fender and slid it forward (just a bit, and hood should stay up ok). I could then remove the screws for the blower motor, and pull it out. Notice the condition of the fan blade as now is a good time to replace if chewed/broken by varmits. You should now (although awkward) be able to clear out the heat bypass flap so that it closes all the way, and then eitehr by reaching in, or by vacuum remove any nesting material found inisde against the heater core. I pulled/sucked a HUGE mess out of my DD here, and now have high speed fan/heat, and did nothing but pull some screws! More power to you if you want to remove the inner fender, drain the coolant, and remove the box entirely, but for a daily driver (or the lazy) this is a great way to do it.

I also checked the resistor coil when I had the inner box apart, but didn't do anything to it except remove some blown nesting and cobwebs. I suppose if you have problems still you might replace it, but I don't know what it controls/regulates.

[ChevLoRay]

After stripping my cab, I have come to the conclusion that it's a pain in the keister to do, but a person really ought to clean out the ductwork once in their lifetime. I found leaves, pine needles, dead bugs, etc., in the ducting and in the housing. The A/C trucks have even more places for the stuff to collect. On top of that, those organic items will retain moisture and that will lead to rust. Oh, you already found the rust? Yeah, me too. Lots of it. Wish someone had been mindful and cleaned it out a while back. Maybe I wouldn't have to change out the firewall before I go any farther.

[67mater]

yeah, you check my build thread for the damage I found and had to fix for the same reason. Also be aware of rot in the bottom the outer heater box and baffle. Lastly, those are not reproduced yet, so fix what you got, or find another.