The Stovebolt Site Forums The Shop Area Interiors Puzzling 1946 heater question

My heater wasn't working in the truck I recently pulled home (after sitting 35 years) so I pulled it out and tested it with the battery and it worked fine. Tried the fan unit connected to the switch in the cab and ground to the frame and it worked. When I slid it into the heater housing however it did not work at all. Went through this cycle a couple of times with the same results. Thinking it's a grounding problem but can't seem to find it... any thoughts?

It has to be a ground problem. The heater is grounded by the mounting bolts thru the firewall. Make sure you have a clean (no paint) connection to the firewall. Also make sure you have a good clean connection from the battery ground to the frame.
A quick test is to run a ground jumper wire from the mounting bolt to the batter ground and see if the fan runs, If so,you have found your peroblem.
Harold

Tried it and it still didn't work = Maybe I have a short somewhere.

If you had a short, you would probably see smoke. I agree with Harold. It has to be a ground issue.

Took it all apart and cleaned everything up. I ran the fan motor and noticed it kept changing speeds as it ran... after a while it was running well. Although I noticed if I tightened the nuts on the fan housing all the way, the motor would not turn. After reassembly, I finally got the heater and defrost motors running through the switches - thanks for everyone's help and getting through my thick head that it was the ground.

When I was initially testing the heater fan, I put the switch all the way down thinking that was high when in fact it was low and the motor wouldn't run on low. Now after running it for a while, low, med & high all work well! Bring on the cold weather (just kidding)

The other option is to run a ground wire from the fan motor directly to the frame. I had to do this with my horn and front parking/turn signal lights on my 54 3100.

Sounds like your fan housing fasteners were putting a bind on the motor. Or the motor itself had gummy bearings. I've seen a number of small motors that took forever to get up to speed, I'm assuming from the lube in the bearings beingi too gummy. Once warmed up they would run fine.