Electrical disconnect

JoeMarine

JoeMarine

Senior Member
I don't want to sound like a real chuckle-head as a "newbie" but to avoid any electrical fires, without an electrical disconnect switch, couldn't a Model A owner just simply disconnect the battery until you want to take it out for a ride? Am I missing something. Thanks in advance for any guidance.
Semper Fidelis
Joe Marine
 
A Disconnect, in my view, isn't needed if the wiring is in good condition.

I would suggest that if you are worried about a problem with the Model A's wiring, then replace the old wiring with a new one and install a fuse from the battery to the main wiring (minus the starter).

Marc
 
A disconnect switch is very easy to install. It might vary but I think most people would recommend that the switch be mounted to the ground cable. (That would be the positive side if your car hasn't been modified.) You can mount it under the hood or under the seat for easier access. Buy a better one, not a cheapo unit as it will fail over time. Good luck & have fun!
 
the cleaner looking installations are under the seat, and buy the good ones from one of the suppliers. you can easily shut it off every time you shut down convientley without having to disconnect the battery and going thru that PIA everytime. have heard of even leaving a cable loose on the battery so its easier to do but when one falls off while driving and the generator gets cooked not fun and a very bad idea...
 
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I have a disconnect on my car and new wiring. It was very easy to install. I did it as more of a theft prevention item. Just one more item that insures that my car doesn't go anywhere without me. I used one of the brackets that mounts on the starter. I hit the switch and bracket with a light coat of satin black rattle can, this helped it to blend in much better. I think its a good item to use and you only have to raise the hood just enough to flip the switch when you walk away
 
Hi Joe,

A. Many varying opinions on installing Model A battery disconnects; & many varying opinions on types of battery disconnects to buy.

B. If you do decide to get one, strongly suggest you get one rated for "6-Volts" & suggest you buy the very best & go "Marine" ...................... no pun intended.

C. Many things electrical sold for boats through reputable Marine Catalogs are more expensive because they are made with higher quality materials & are designed for high humidity areas & salt water exposure.

D. Many battery disconnect manufacturing companies recommend disconnecting the ground wire; but here again, varying opinions among Model A owners.

E. Anyway, just remember there is nothing like having a "cheap" plastic auto-type disconnect fail on your Model A while 150 miles from home, late at night with no lights, & on a two (2) lane highway with no shoulders -- plus you forgot your tool box.

F. Mine is a keyed switch with a heavy duty removable key with the switch accessed on the driver's side, (near the front edge of the front seat), through the floor board, & under the floor mat.

G. Best thing is you decide what you want for your Model A.

Hope this helps.
 
Some of the disconnect switches marketed in past years were very poor quality. All the starter current has to pass through it when starting the car. They can overheat and burn up. And what you don't want is it disconnecting while you are rolling down the road as the battery will then be disconnected from the cars electrical system and the generator will burn up.

My personal view is to install the fuse mod on the top of the starter. When you secure the car for the day lift the fuse and stand it on its head in one end of the clip. This way all the car's electrical except for the starter is disconnected from the battery.

Tom Endy
 
I don't use one. I agree with Tom. Really there isn't much to cause harm. Even if the reverse current relay sticks I doubt you'll see a fire. Warm perhaps. The other issue with the battery disconnect switch (and fuse) is that if the generator goes open circuit it will burn up as Tom said. The other issue is in an open circuit it will go to quite high voltage. You'll a lose a brake light if it's daytime. More over as the generator goes high the coil will over-saturate and you'll lose spark. The engine will stop firing and the fuel will load up in the cylinders and the muffler that is too close to the manifold.
As the engine/car slows the generator voltage falls and the coil begins to fire again.
Kaboom!

My A did this as the original owner put to long a fuse in the holder. The screw that holds the clip kept the fuse from "clicking" all the way into the fingers. Hit a bump and it pops out of the clip.
Generator did survive btw.
As to the muffler, let's just say Aries makes nice ones.
I still fuse but may go to a fusible link. When they burn you get a fair amount of smoke as the vinyl burns..<grin>
 
Use a good quality switch in the ground cable mounted in the floor for quick access while going down the road. Ever try to disconnect a battery cable or lift the hood at 40 mph.
It's pretty nice to have when you've got a stuck starter switch or burning wiring.

PS
If every thing is right you wouldn't Insurance,seat belts or a fire extinguisher either.
Bill
 
When this subject was being discussed many times previously, I think it was one of the Mike's posted a pic of the proper main cutoff switch to use.
IT HAS TWO CIRCUITS. A heavy one to handle the battery cable and a small one to handle the generator wire. A stock model A will keep running (for awhile till something burns up) if the main battery cable is disconnected.
 
Pete said:
When this subject was being discussed many times previously, I think it was one of the Mike's posted a pic of the proper main cutoff switch to use. IT HAS TWO CIRCUITS. A heavy one to handle the battery cable and a small one to handle the generator wire. A stock model A will keep running (for awhile till something burns up) if the main battery cable is disconnected.
Click to expand...

Yeah, Pete, it was me. Here it is again:

A battery "shut off" does exactly that. It disconnects, or "shuts off" the battery from the electrical system. The engine will continue to run, with ignition powered by a still turning generator, alternator, or magneto.

A "Kill switch" is specifically wired to stop the engine. It may do so by disabling the ignition, fuel supply, or anything necessary to maintain engine locomotion. It does not necessarily disconnect the battery.

If you want both functions in one switch, you need a DPST switch like this, that disconnects the battery AND interrupts an essential circuit in the engine, like the gen/alt, the fuel pump, or the ignition.

Some racing rules require BOTH, a switch like the one below-
The large terminals are for battery disconnect, the two smaller for interrupting an essential "run" function as explained.

This is actually the ideal way to put a switch in an A, but, like most things electrical, misunderstood (including by vendors and their advertising) and thusly not used.
51eDyXGGpLL._SL500_.jpg
 
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