Battery Disconnect / Isolator

I use a switch in all of my cars. When I got my very first one, it was fitted with one of those horrible ones that fit on top of the battery - the ones with a green wheel on them. NEVER use one of those. Their life is very short and they can leave you stranded on the side of the road. Don't ask how I know.
 
Mine came with the car and is mounted on the side of my seat riser. I love it and I think every Model A should have one.
 
Y-Blockhead said:
I believe the OP's question was answered in post #3.
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Actually the first answer was given in Post #2. Does anybody recognize where Gary copied that page is from?

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Ground side or supply side really not much differance. Most of mine are on the suply side because they need to meet the rule book for NHRA drag racing and there very clear on the master switch wiring. I know that were not racing here but 50 years of use with no ill efects I think putting the switch on supply side is fine, everything else in your car is switched on the supply side with no problems :)
 
Synchro909 said:
one of those horrible ones that fit on top of the battery - the ones with a green wheel on them. NEVER use one of those. Their life is very short
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I don't get the picture, maybe there's different quality switches. I keep hearing horror stories about the battery mounted switches. I have one that's been on a vehicle (not a Model A) for 10 years and never a problem w/it. Vehicle gets used about once a month.
 
The battery disconnect switches used on boats are the best quality. Probably overkill for a car. The marine switches are available that disconnect both sides of the battery. $$$$
 
If you have a 30 amp fuse installed, are you expecting your starter switch to fail. IMHO, that would be the only reason to install a battery cutout.
 
What does the fuse have to do with the starter switch? Other than being mounted on it.Any number of things can go wrong and caues a problem while sitting around.Most common ones I have been seen have been sticking cutouts,and sticking brake light switches.I've seen two problems from switches mounted in the hot side.One in an A,mounted on the firewall.The cable worked it's way out of the crimp and bounced around arcing until it wedged itself in a solid spot and blew the battery up.Another was in a Comet drag car,(Maverick) and the switch was mounted where the gas cap used to be at the rear of the car.The trunk was full of camping stuff,with a couple cans of gas and a propane bottle.That fire even melted the rear tires on the trailer it was on but the fuel cell in the trunk never burned.I've never seen a credible reason to put the switch in the hot side,it always seems to be,well they told me to.
 
To me, it is common sense to put the switch on the earth (ground) side. That isolates EVERYTHING - no half measures.
 
I second the suggestion to locate the cutoff switch near/through the seat riser. The new-to-me Fordor slant had it mounted through the firewall next to the clutch pedal. The seller didn’t mention its existence, and twenty minutes after writing him a check I accidentally shut off the current with my foot while approaching an intersection in Houston. Everything turned out fine, and I had a cutoff switch relocated.
 
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In 1972 I had a wiring harness fire in my first Model A. Thankfully the damage was minimal. I’ve installed a battery disconnect switch in every Model A I’ve owned since that incident. Lesson learned.

Easy access to the switch in an emergency is often overlooked. Cutting the power could be the difference between minimal damage and total loss. When seconds count the fire department is minutes away.

Some models can be challenging to find a location for the switch. There are some really clever solutions out there. The attached photo is my current 1929 Tudor. I can easily reach the switch from the driver’s seat.
 
With the switch OFF everything IS isolated except for the short length of cable between the battery and the switch no matter what side the switch is in, OFF breaks the path for currant.
Just like your headlight switch, OFF and no currant between the switch and the light
The switch that's in the currant supply side ;)
Sloppy workmanship, bad or loose conection, and unprotected conections points are just asking for trouble at some point in time no matter how you wire a switch :)
 
A couple of months ago in the Restorer or Model A News there was an article about a Model A the burned due to the clutch rod coming in contact with the power cable. If there was a S/O switch on the ground side, a lot of damage could have been prevented. Another fella had the battery hold down come in contact with the negitave terminal. Same situation.

I realize these are not common occurances, but they do happen.

BTW, I thought I would mention, our club does have genuine Ford Model A Smoke available in limited quantities if you inadvertently let yours out... don't use the Lucas smoke that is on the market!

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