Wiring Diagram and Background for Robbins & Meyers Twin/Dual Motor Casement Window Fan

[Isaiah Sampson]

NOTE THIS IS NOT A QUESTION! JUST POSTING POSSIBLY USEFUL INFO

While restoring a Robbins & Meyers dual-motor casement window fan, I made a diagram for re-wiring the two switches and am sharing it here in case it is useful to someone in the future who neglects to document the wiring when disassembling their own similar fan.

In my case, both switches had soldered short wires about 4" long or so that were then spliced to the motor wires with wire nuts. The switches are connected to eachother by one very short (about 2") soldered wire, so if you are trying to preserve the existing wiring, be careful manipulating the switches. All wiring was cloth-wrapped and stranded aluminum.

I did not replace any of the existing wire as it did not have any exposed aluminum strands within the cables between switches and motor, only where insulation on individual wires at the switches had dried and broken off, and I simply wrapped that in electrical tape.

REWIRING DIRECTIONAL WARNING

In case you choose to replace all wiring, be warned that the intake/exhaust direction change switch has symmetric wire-soldering tabs about each axis and you could accidentally reverse the wiring when re-soldering. In my sketch, the "Out" setting on the directional  switch and the "high" setting on the speed/on/off switch are at the right of the sketch.

REUSING EXISTING WIRING WARNING

As mentioned above, I did not replace any wiring. The existing cables (cloth sheathing around cloth-wrapped wires) were rigid due to to drying out of the cloth and could not be bent without breaking off the cloth. I had another person hold the frame steady while I rotated each fan motor and contorted them to pull the cables through the existing rubber guiding grommets without bending it. Secondly, the guiding grommets were meant to hug the cable closely, and in the cable's dried out state, the cloth began to rub off/disintegrate in places as it was pulled through. Before reassembly/rewiring, I advise that all grommet holes be enlarged with a drill bit 1/16"-1/8" larger than the existing hole. This will avoid friction and also help pass through any cable that you had to wrap in electrical tape. Having done so, I did not damage the cloth sheathing at all during reassembly.

Here is my post trying to date the fan with more photos; my thanks to those who responded to me:

https://new.afcaforum.com/index.php?/topic/7547-dating-robbins-meyers-dual-motor-window-fan/

Robbins and Meyers Twin Motor Casement Fan Wiring Diagram.pdf