Overdrive electrical problems

[Lothar]

You know how a simple task can turn into a nightmare? Well, I created quite a situation for myself. The speedometer cable on my 1950 Champion was bouncing, so I decided to lube it. Simple job, right? I disconnected it at the tranny, pulled it out and up, ran some special speedo cable lube into it, worked it a little bit, and, with my son's help, started to slide it back down along the firewall to get it back in. That's when things went bad.
I apparently caught the cable on the OD relay. It created a direct short, apparently from the relay to ground on the body (not sure)and started cooking the cable and the fresh lube in it. By the time I scrambled out from under the car and disconnected the Neg. Battery cable, which was already loose (about ten seconds or so), smoke was bilowing from the lube cooking, the cable sheath was glowing red and kinked from the heat. Suffice to say that, even though the cable was ruined, I'm lucky I didn't burn up the whole car. Lesson learned there.
The problem I have now is that the overdrive doesn't work. The fuse on the OD relay is OK, but I assume I cooked it inside. How would you test one of these things with a multi-tester? Could I have damaged the solenoid or something else? Since the relay is a $95 part, I hate to replace it if I don't have to do so. Any advice is appreciated as always.

1950 Champion
Holdrege NE

[Roscomacaw]

Well,

If the cable fried and it didn't blow the fuse, you had to have shorted to the terminal where the power attaches to that relay. That being the case, I'd be worried about some of the wires associated with the overdrive system being fried and maybe shorted together.
That speedo cable was glowing red and that means it was carrying ALOT of current! That also means that the power lead going to the OD relay was taxed WELL beyond what it's meant to carry! And THAT means that it's quite likely that that wire burned thru it's insulation and maybe into the insulation of any wires bundled with it.[xx(]
That power wire goes straight to the battery side of the starter solenoid. It's been some time since I looked under the hood of a '50 but that wire may or may not be incorporated in the main harness. For your sake, I hope not! If it IS part of the main harness, there's a fair chance it damaged other circuits - if it's not - or if it's incorporated in a seperate harness for the OD system, then it won't be as bad.
But at best - you'll have to remove that wire from the relay (bat disconnected of course) and check the condition of the wire, the (probably now anneald) terminal ends and clean up the terminal screw, the terminal on the starter solenoid and the health of any other wires that are bundled with it. And next time, disconnect the battery anytime you're playing around with bare metal behind the istrument panel OR where there's bare terminals on the firewall.[:I]

Miscreant adrift in
the BerStuda Triangle

1957 Transtar 1/2ton
1960 Larkvertible V8
1958 Provincial wagon
1953 Commander coupe

[Roscomacaw]

And I forgot to mention........ anytime you disturb the fuse on that relay, when you put it back, it may not make good contact. I JUST had the same thing happen with my truck. I didn't have anything really adequate to clean up the fingers of those fuse-holder fingers and I ended up using a jumper wire to get me home with the OD.
50 years ago, the inside of those fingers were nice shiny metal. Now they ain't like that and it's tough to clean them up and keep them that way. A bit of petroleum jelly on the fuse ends will help stave off corrosion after you get everything clean.

Miscreant adrift in
the BerStuda Triangle

1957 Transtar 1/2ton
1960 Larkvertible V8
1958 Provincial wagon
1953 Commander coupe

[Lothar]

Mr. Biggs
Thanks for the analysis. I imagine that you're right about the wires. I take it by your response that you think its more likely the wiring than the relay, since the fuse didn't blow.
The wiring is pretty sketchy after fifty seven years, and I plan to replace the entire harness, anyway. There is a separate OD harness, which hopefully includes the power wire. The starter works fine, so that didn't get burned.
Clearly, I learned a valuable lesson about the power of 6 volt electricity. I am being much more careful now. I'm not sure about the term for it, but isn't there some sort of fuse or circuit breaker you can put on a battery terminal? Would that have helped in this situation?
The car is across town in a friend's garage, so I can't just run out and look at it. I will also check the contacts on the relay fuse. Thanks again.


1950 Champion
Holdrege NE

[Roscomacaw]

Yeah - voltage has nothing to do with it in the realm of power that common cars and trucks use. ONE volt could cause the same woes if there's enough AMPS behind it.

I think you're talking about a fusible link and that might offer some protection - to the whole car, for that matter. Of course, just a simple 20amp in-line fuse in that hot wire to the relay would've saved you from what you did.

I'll be really surprized if you came back to report that no wires were damaged![:I]

Miscreant adrift in
the BerStuda Triangle

1957 Transtar 1/2ton
1960 Larkvertible V8
1958 Provincial wagon
1953 Commander coupe