[57taskforce]

Ryan, let me know what you find on those hubs.



This afternoon I went thru some gremlins in the hvac wiring I’ve had since I brought it home in 2015. The blower never has run since I bought it. Back in July I started messing with getting the blower motor running. I got side tracked once I got power to the purple motor supply wire. The motor still wouldn’t come on with power, so I figured it was bad and put it on the back burner, then it got cold and I figured heat might be kinda nice. I was wrong the motor wasn’t bad and I didn’t have consistent voltage at the motor feed.

After applying power directly from the battery to the motor it fired right up. I then went thru the whole system with my fluke testing voltages, continuity and grounds. Then I went thru all the wiring removing each individual contact from each plastic connector and cleaning them with emery cloth. Basically there were a couple problems.

First there were a few connections that had light corrosion on them and had mediocre continuity. The ground on the motor relay wasnt making good contact to the relay housing, preventing high speed on the fan. The biggest thing I fought was loosing voltage as soon as the motor feed was connected to the motor. The voltage would drop to 0 no matter what position the switch was in. This is what lead me to cleaning every contact.

Eventually I got it to run on the relay in the high position. Still nothing when trying to run on the resistor. If I jumped the resistor power between the dark blue wire from the resistor and the purple motor feed wire at the relay connector I could get the fan to run on the resistor. It would not run on the resistor without jumping power at the relay connector.

It came down to the relay. So I figured what the hell, I’ll open it up and see what gives. The relay handles current when the coil is both de-energized and energized. When de-energized it handles the current coming from the resistor to the motor. When energized(high position on the switch) it handles a full 12 volts required to spin the motor at full speed. The contacts on the de-energized side of the relay, that handles the current when it’s running on the resistor were dirty/lightly corroded. The bad continuity in the contacts wasn’t able to handle the amps required to spin the fan thus dropping the voltage to 0 at the motor connector. A little cleaning and it’s working good. If you take the relay out of the metal case you can watch the contacts open and close and see for sure where the issue is. I should have taken pictures but by the time I got to this part of it all, it was starting to get pretty cold and dark was approaching. I need to put it all back together tomorrow and hook the heater hoses back up. It’ll be nice to have heat!

I don’t know if I ever mentioned it or not but the majority of the cab wiring including the fuse box and even most of the under hood wiring is actually from a 72 C10 I Parted out 5-6 years ago. The original wiring in the K20 was in really bad shape. Gum wrapper fuses, several melted wires etc. I wasn’t about to build the truck then burn it to the ground with crap electrical. I had to re-pin a few of the harnesses and add things like the back up light wiring for the manual transmission, but all in all it’s worked out really well. This and getting the back up lights working are the only real electrical issues I’ve had. Backup lights were a bad fuse panel feed connection, that one took a while to figure out as well.

I doubt any of this makes much sense without pictures, more than anything I wanted to document it in case I forget what the hell I had to do down the line if there’s any more issues.