Convertible Top Switch Hazard

by John Grady

The following will be of interest to anybody with 1957-67 (at least ) Mopar convertible.

While riding around with the top down in my 1957 300C, I noticed ammeter fluctuating wildly to full charge for a full second or so then waving around and then normal. I realized later in the drive, it was repeating about every 5-6 minutes. So I made mental note, figured it was the mechanical regulator, must be burned points again, and continued the ride for 2-3 hours.

Once I got home, the top would not go up. It moved about a foot and just stopped. I tried again a few minutes later and it went up and I noticed the circuit breaker was still hot. I pulled off the battery cable as fast as I could.

As I checked into the situation, I got into the convertible top switch. The switch was actually “stuck on”  in down direction, so the top was continuously trying to go down for 3 hours! But the 20 amp circuit breaker would open after a second and cut off the power. Otherwise I could have had a harness fire or burned up top motor, generator or regulator.

The convertible top wiring drew a lot of power (30-40 amps) for a second because the top pump motor was stalled dead (the top was full down). The circuit breaker opened, then the generator replaced that power into battery, then things went back to normal until the breaker closed again, repeat over and over. The reason the ammeter shows CHARGE, not discharge, is because the top wiring connects directly to the battery + lead; the power to the top does not pass through ammeter. So when running the top motor, it lowers the  battery voltage, the regulator turns on the generator or alternator to “ full on”, the ammeter shows a big real charge but cannot keep up with that short, but it tries, and so you see a big full scale charge. This raises hell with regulator and generator and top motor and could burn them out.

So decided I needed a new switch. I found then on Ebay at $220 each (!!!!). So I found a 40A standard  ‘toggle switch” SPDT and checked the hole in the dash and the bezel etc, and thought by drilling the hole slightly oversize, looked like it could be made to work. But it would have a non-stock looking toggle handle. I had gotten that kind of switch before, for a 64 Mustang top motor from hydro E lectric , an online convert parts source. I also had gotten 300 hoses from him.

Since I had the old switch out, I decided I had nothing to lose so got it open by carefully prying back 4 die cast fold ins with small sharp dike or wire cutter, small screwdriver. Once open, the switch is pretty simple with a V shaped contact, which looked OK. It sits on the middle feed contact and moves by the lever bat “end “ sliding on inside of the V. But it all was loose and copper V was just flopping around. Somehow it had fallen down and “made” the close side of switch. It looked like missing a spring or something.  Mystified, I thought how can this ever work? Then I noticed the slider part of toggle is made of Nylon which looks “swaged” into the metal bat that is the outside handle you move. But with a closer look, it is supposed to slide out. Inside the hollow Nylon and up into the hollow bat is a tiny spring like a ball point spring but maybe 1/16“  or 3/64” diameter. Repeat tiny. The Nylon is supposed to slide out, pressed out by that spring which would hold V straight in middle and hold bat straight out. I could see now it was stuck in there by rock hard grease!!! This is the same affliction I had with wiper motor park cams -- hardened grease on Nylon parts. So I cleaned out with WD 40, put 30 W oil on it, reassembled and it works great.

So, try the toggle switch on your top. If it is obviously real floppy in the middle, the spring may be getting stuck, or is stuck. When fixed it will self center pretty good –you can feel spring action. I had noticed mine was sort of sagging down, lot of play, but it worked so I let it go. Now I know better!

Plus I know the hard way, that on 57-59, if you push “down”  switch while top is still latched, (or it “pushes itself”) the big aluminum main arm in back will snap right off at the pivot bolt……talk about unobtanium.

It is possible on other years the convertible top switches vary, but the design I describe here was common. I could see power window switches doing this too. So this is my heads up! Stay safe.