Re: Don’s 1937 (120) 138CD Deluxe Touring Limo

Posted by Don B On 2024/9/16 22:36:49

Got to tinkering in the garage and decided to once again investigate the operation of my heater and defroster switch/rheostats. Only one of which is correct for the car (thanks to Flackmaster for confirming). That’s okay as I have another correct one on the way and the better of my two existing was a correct one.

The existing correct switch was pretty rough in its operation, not smooth, not consistent electrical resistance, you name it. So, I disassembled and cleaned thoroughly. I then confirmed that the resister coil was 1.7 ohm end to end, which is about what I was expecting.

Here’s where it gets interesting. When I put it all back together, I had between 28 to 30 ohms across the terminals when adjusting through the range. Hmmm….

So, I ohmed out the resistor coil again…1.7 ohms end-to-end. Then ohmed the swipe contact to its terminal…0.1 ohm. So far so good. Then, I ohmed from the end of the resistor coil to the other terminal…..28 ohms. Now this point is connected by a brass rivet and everything is very solid physically. So, I then ohmed from the resistor to the terminal side of the rivet (not the terminal)….0.1 ohm. Aha! Next I ohmed from terminal side of the rivet to the terminal….28 ohms.

I now had a solid conclusion. After 87 years, there is a build up of crud/corrosion between the very solid physical connection of the rivet and the terminal. So, I got out the soldering iron and soldered the rivet and the terminal….Problem solved.

I should have taken pictures before I soldered, but didn’t think of it…here’s the after picture, though.