The Ford Barn

Synchro909 · 05-21-2026, 06:30 PM

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.

Jim16A1 · 05-21-2026, 11:46 PM

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.

Randy in ca · 05-22-2026, 01:04 AM

Quote:

Originally Posted by Y-Blockhead

I believe the OP's question was answered in post #3.

Actually the first answer was given in Post #2. Does anybody recognize where Gary copied that page is from?

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Y-Blockhead · 05-22-2026, 01:17 AM

Quote:

Originally Posted by Gary WA

Did you ever get the correct answer to your question???!!!

Quote:

Originally Posted by Randy in ca

Actually the first answer was given in Post #2. Does anybody recognize where Gary copied that page is from?

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Actually, no. The first correct answer is in Post #3, on the ground wire. Post #2 shows the switch on the supply wire.

Bruce of MN · 05-22-2026, 04:49 AM

Quote:

Originally Posted by FFOG

"Old Ugly" What a great name!

I don't think he is very old!

Bruce of MN · 05-22-2026, 04:58 AM

Sponsored Links (Register now to hide all advertisements)

Another thread here with good ideas.

https://www.fordbarn.com/forum/showt...ch#post2068301

Tom F OHIO · 05-22-2026, 08:58 AM

Quote:

Originally Posted by Y-Blockhead

Tom, here is a different angle. That is the brake crossshaft just below it.

Thank You.

Phil Brown · 05-22-2026, 10:04 AM

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

katy · 05-22-2026, 10:25 AM

Quote:

Originally Posted by Synchro909

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

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.

nkaminar · 05-22-2026, 01:28 PM

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. $$$$

AL in NY · 05-22-2026, 04:22 PM

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.

The Master Cylinder · 05-22-2026, 04:33 PM

Quote:

Originally Posted by AL in NY

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.

See post #6

Keith True · 05-22-2026, 04:51 PM

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.

Synchro909 · 05-22-2026, 07:04 PM

To me, it is common sense to put the switch on the earth (ground) side. That isolates EVERYTHING - no half measures.

old31 · 05-23-2026, 02:13 PM

Quote:

Originally Posted by FFOG

"Old Ugly" What a great name!

Oh, it is more than a name. He really is old and ugly!

David in San Antonio · 05-25-2026, 04:15 AM

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.

Wello · 05-25-2026, 07:37 AM

IMG_2157.jpg

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.

Big hammer · 05-25-2026, 08:17 AM

Quote:

Originally Posted by Synchro909

To me, it is common sense to put the switch on the earth (ground) side. That isolates EVERYTHING - no half measures.

X-2 ! Then you only need to be careful with the battery ! You don’t want to cross the posts with something metal !

Phil Brown · 05-25-2026, 11:33 AM

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

Y-Blockhead · 05-25-2026, 12:00 PM

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!

05-21-2026, 06:30 PM	#21
Synchro909 Senior Member Join Date: Jun 2014 Location: Melbourne, Australia Posts: 8,432	Re: 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. __________________ When all is said and done, more is said than done. That's why we judge people on what they do, not what they say. I sometimes wonder what happened to the people who asked me for directions. If I am not in trouble, I've done something wrong.

05-21-2026, 11:46 PM	#22
Jim16A1 Junior Member Join Date: Sep 2025 Posts: 28	Re: Battery Disconnect / Isolator 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.

05-22-2026, 04:58 AM	#26
Bruce of MN Senior Member Join Date: May 2010 Location: VA Posts: 2,047	Re: Battery Disconnect / Isolator Sponsored Links (Register now to hide all advertisements) Another thread here with good ideas. https://www.fordbarn.com/forum/showt...ch#post2068301

05-22-2026, 10:04 AM	#28
Phil Brown Senior Member Join Date: May 2010 Location: Santee Calif. Posts: 692	Re: Battery Disconnect / Isolator 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

05-22-2026, 01:28 PM	#30
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 6,847	Re: Battery Disconnect / Isolator 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. $$$$ __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.

05-22-2026, 04:22 PM	#31
AL in NY Senior Member Join Date: May 2010 Location: Southern Upstate New York Posts: 1,236	Re: Battery Disconnect / Isolator 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. __________________ AL in NY

05-22-2026, 04:51 PM	#33
Keith True Senior Member Join Date: May 2010 Location: Epping N.H. Posts: 3,689	Re: Battery Disconnect / Isolator 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.

05-22-2026, 07:04 PM	#34
Synchro909 Senior Member Join Date: Jun 2014 Location: Melbourne, Australia Posts: 8,432	Re: Battery Disconnect / Isolator To me, it is common sense to put the switch on the earth (ground) side. That isolates EVERYTHING - no half measures. __________________ When all is said and done, more is said than done. That's why we judge people on what they do, not what they say. I sometimes wonder what happened to the people who asked me for directions. If I am not in trouble, I've done something wrong.

05-25-2026, 04:15 AM	#36
David in San Antonio Senior Member Join Date: Sep 2022 Location: San Antonio Texas Posts: 713	Re: Battery Disconnect / Isolator 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. __________________ David in San Antonio Late ‘30 Deluxe "Wretched Roadster" 1931 Slant Windshield Fordor “Earl Gray” Alamo A’s Club

05-25-2026, 07:37 AM	#37
Wello Senior Member Join Date: Apr 2011 Location: Paradise, CA Posts: 107	Re: Battery Disconnect / Isolator IMG_2157.jpg 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.

05-25-2026, 11:33 AM	#39
Phil Brown Senior Member Join Date: May 2010 Location: Santee Calif. Posts: 692	Re: Battery Disconnect / Isolator 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

05-25-2026, 12:00 PM	#40
Y-Blockhead Senior Member Join Date: Jul 2011 Location: Redondo Beach, CA Posts: 7,288	Re: Battery Disconnect / Isolator 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! Last edited by Y-Blockhead; 05-25-2026 at 12:44 PM.