backup light switch

[DonaldSmith]

To work the backup light on my 47 DeSoto, I bought a microswitch with a lever and roller at the end. I looked for places to mount the switch, since the transmission has no provision for a backup light switch. I looked at various places in the shift linkage. I gave up with locating the switch at the transmission. Too dirty, and hard to get at.

Under the hood, at the steering column, is a sector that rotates up and down and slides back and forth, with the motion of the shift lever. I tried mounting the switch so that the sector would come up and hit it in the reverse position. But there was not enough back and forth motion, or too much slop, to avoid hitting the switch in the "Low" or "Power" position. (Up and forward; it's a clunk-o-matic).

Moving the shift lever back and forth moves a lever under the steering column which works a shift rod. In reverse, the rod is forward. I added a fender washer and double nuts to the end of the rod. I mounted the switch under the steering column so that the washer would work the switch when the shift lever is in reverse and the rod is forward.

That's what I did.

If I had a conventional three-speed, the switch would also be "on" when the transmission is in 1st. But there is no 1st position for the semi-automatic. If I had a three-speed, I would put another switch in my original position, where the sector rotates up, which would turn the switch "on" in reverse and second. The switch below the steering column would be "on" in reverse and first. I would wire the two switches in series, so the backup light would come on only in reverse.

That's what i would do.