Technical Question for the electrically inclined.

I'm working on papaw's 40 Ford again (water pumps this time) and I am planning on rewiring the firewall-mounted solenoid. I say "rewiring" because someone else wired it in and it wasn't correct (to say the least). The 40 Ford Coupe originally had a button on the dash that completes the circuit (to chassis ground) to energize the starter. Later solenoids complete the circuit on the positive side to energize the starter motor. My question is: "can I wire the solenoid to where the button on the dash can be used to close the circuit and energize (to ground) the starter? I'm fairly certain it can be done by mounting the solenoid to an insulating material then by mounting it to the firewall. My concern is: "will it be safe and reliable?" The system has been converted to 12 volt. Has anyone else done this? It's just 12 volts going through a coil, right? It doesn't matter which way it goes, right?

 

Should work fine. The dash button is just a switch, closing the circuit to the solenoid.


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I would worry about something grounding it accidentally.
wire in a relay. easy, reliable and safe.

 

Standard Ignition makes a 12 volt version of the original starter relay, SS-587.

https://www.amazon.com/Standard-Motor-Products-SS587-Relay/dp/B000CQ44P4

 

You are over thinking it.
The 1940 stuff should work just fine.

This stuff does not know the difference between + or -.
It only knows hot and ground. Just do not " ground to the hot" or vise versa.

There is no reason to insulate the sylenoid. It's a contained unit. If there's a problem there like sparking or smoking.... you have a dead short somewhere.

Get the'40 shop manual.

 

For 10 bucks, this is a definite no brainer.

 

"You are over thinking it." I have a tendency to do that. Some say I'm paranoid. I look at it like this: "Foxes are paranoid, Possums ain't." How many dead foxes do you see on the side of the road? Now, how many possums? (and yes, I know the correct spelling is "opossum"). Also, there's the fact that it's papaw's and I would hate to know I harmed it in any way so that's why I'm extra cautious. Thanks for the reply. I will look into getting a shop manual.

 

Just replace the solenoid with THIS ONE. Make the underhood like the original.
Glad to see this post, didn't KNOW about this solenoid! Thanks!

 

I got a two prong starter button that fits the '40 Ford hole in the dash. Was told that it came from a '51 Ford.

 

https://www.amazon.com/Standard-Motor-Products-SS587-Relay/dp/B000CQ44P4
Why the hell did that quadruple in price overnight?
Must of been priced wrong, $23.79 at Rockauto.