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Old 07-29-2020, 11:20 AM   #1
aquadave
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Default Battery Isolator switch

I have a 1930 Model A with 6 volt positive ground system.
I have to take the fuse off of the starter as soon as I shut the engine off or the battery will drain.
I want to install a battery isolator switch but can't find a good drawing of how it should be installed in this system.
I'm planning on installing the switch at the base of the drivers seat just behind the access to the battery.
I'd really appreciate some help with this.
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Old 07-29-2020, 11:23 AM   #2
aquadave
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Default Re: Battery Isolator switch

By the way I might not be calling this switch by the right name. Basically I want to install a switch that cuts power from battery to the car.
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Old 07-29-2020, 11:35 AM   #3
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Default Re: Battery Isolator switch

I have one on my 29 Roadster that works Great!! I put it inside the engine compartment. Came with a mounting tabe. It cuts ALL power to the car and is out of site. Got it from Bert's in Denver. I am going down to my shop sometime this afternoon and can take a picture of it if you would like. It "breaks" the positive lead. I believe it uses one of the oil pan bolts to mount but will check it.
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Old 07-29-2020, 11:41 AM   #4
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Default Re: Battery Isolator switch

Thank you Jim that would be great. I have a switch already but just not sure how to wire it in.
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Old 07-29-2020, 12:09 PM   #5
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Default Re: Battery Isolator switch

In series with the battery. Either side of the battery will work, however, there has been a lot said of the benefits to putting it on the positive (ground) side. Really super simple as far as what connects where. The hard part is where to physically put the switch in a convenient place and the resulting routing of the rather heavy gauge wires to/from the switch. A lot has been written and discussed on that, you might get a lot of hits if you used the search function and sifted through the discussions. One thing is certain. Unless you have a show car for judging, it is certain that you DO need a battery shut-off switch.
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Old 07-29-2020, 01:04 PM   #6
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Default Re: Battery Isolator switch

Hi Dave,
Best thing you could ever do for your old car. I even have one in my E Type as well as my 250SL Pagoda.
Jim has his in the engine bay, which means, you have to open the hood to turn off the Ďmainsí
Unfortunately, this becomes a chore and eventually, you stop using the cut off switch.
Each to his own, but I have put mine in the cab, close to or under the seat. So this have become part if my start and shut down procedure, like in an airplane.
Master switch ON
Fuel ON
Ign ON
etc

So every time you walk away, you know the car is DEAD and will hopefully stay dead until you get back.
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28 Model A RPU, 29 Chevy Phaeton, 67 E Type FHC, 67 250SL Pagoda, 83 911 SC
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Old 07-29-2020, 01:52 PM   #7
Patrick L.
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Default Re: Battery Isolator switch

Where you want to install the switch is a good place, easy to get to. Make sure the wires are heavy enough, no lighter than #1. It doesn't bother me which line the switch is in.

But, my main question is;;; why not find and fix the draw ?!
1. That off a battery lead
2. connect a test light or voltmeter between the lead end and battery terminal.
3. If there is a draw it will show on the meter or light the light
4. keep disconnecting things until the light goes out or the meter reads 0. Thats your draw. Fix it. [ Its probably the stop lights, dash light, or generator cut-out]

Last edited by Patrick L.; 07-29-2020 at 05:49 PM.
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Old 07-29-2020, 02:41 PM   #8
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Default Re: Battery Isolator switch

Just tried uploading a couple of pictures but no luck. But the swith attaches to one of the bolts that hold the starter on (the one you actually see when you look at the started.. After you have attached the switch to the starter ( just ONE bolt) you cut the wire that goes from the Negative post of battery to the starter, strip the ends that are cut and attach them to the switch. Half hour job. Then when you put the car to bed for the night just snap the switch off and close the hood.
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Old 07-29-2020, 02:43 PM   #9
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Default Re: Battery Isolator switch

Send me a PM if you have any trouble or questions
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Old 07-29-2020, 02:50 PM   #10
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Default Re: Battery Isolator switch

reduced.jpg think I got it
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Old 07-29-2020, 02:51 PM   #11
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Default Re: Battery Isolator switch

I agree with Patrick, why not find and fix the problem.
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Old 07-29-2020, 03:12 PM   #12
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Smile Re: Battery Isolator switch

I would agree with you but when it comes to electrical I'm not the swiftest.
I replaced the cutout switch on the generator with a switch that has the diode in it but the drain got worse.


This was my Dad's car and he told me to always remove the fuse or the battery would go dead. I ignored that advice for awhile and had no trouble but then things changed.
I'm trying to bone up on my electrical skills but I still want to install the switch as a theft deterrent and Yes, I know that the average thief has no idea how to start or drive this vehicle.
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Old 07-29-2020, 03:13 PM   #13
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Default Re: Battery Isolator switch

Quote:
Originally Posted by Jim M View Post
Attachment 437363 think I got it
Thank you Jim. I really appreciate your efforts.
I'll keep everyone up to date on my progress.
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Old 07-29-2020, 03:19 PM   #14
aquadave
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Default Re: Battery Isolator switch

Quote:
Originally Posted by Bill G View Post
In series with the battery. Either side of the battery will work, however, there has been a lot said of the benefits to putting it on the positive (ground) side. Really super simple as far as what connects where. The hard part is where to physically put the switch in a convenient place and the resulting routing of the rather heavy gauge wires to/from the switch. A lot has been written and discussed on that, you might get a lot of hits if you used the search function and sifted through the discussions. One thing is certain. Unless you have a show car for judging, it is certain that you DO need a battery shut-off switch.
Hi Bill. Unfortunately I don't understand what you mean by "In Series".
I have a switch that has one long red lead and one long black lead.
Both are battery cable gauge.
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Old 07-29-2020, 03:30 PM   #15
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Default Re: Battery Isolator switch

Color of the wire is not important. Where the positive side of the battery connects to the frame, unhook and set aside that cable, and place one of the wires from the switch To the battery where the cable was, and connect the other switch wire to the frame. Now the switch is in series. Figuring out where to mount the switch is totally up to you and your preference. The cable you removed and set aside, you can toss it or save it. It is not used with the switch.
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Old 07-29-2020, 06:33 PM   #16
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Default Re: Battery Isolator switch

The color of the wire could be important. If it is a red wire, connected to the battery/starter it is probably sized for a 12 volt system and not a 6 volt system. Is the battery installed with a positive ground, as it should be? If the fuse is out and the battery still is draining down your car has a wiring problem or a bad battery. You should do the right thing and find the problem and fix it.
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Old 07-29-2020, 07:47 PM   #17
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Default Re: Battery Isolator switch

Installed one using the opening in the motor mount behind the starter on my 28 Phaeton. Negative cable from starter to switch, another cable from switch to negative connection of battery. Rubber boots not shown were installed on switch contacts. Open hood to access not a big deal.
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Old 07-29-2020, 09:34 PM   #18
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Default Re: Battery Isolator switch

The battery should not be drained when not running. The disconnect switch can be a good safety device but the reason for the current drain should be found.

Marc
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Old 07-29-2020, 09:47 PM   #19
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Default Re: Battery Isolator switch

Aquadave, if you have an alternator in place of a generator, you may have an internal leakage in the alternator and will discharge your battery in a few days. Best to pull the fuse mounted on the starter, or install a disconnect switch like you plan to do.
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Old 07-29-2020, 09:55 PM   #20
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Default Re: Battery Isolator switch

Quote:
Originally Posted by RollinRock View Post
Installed one using the opening in the motor mount behind the starter on my 28 Phaeton. Negative cable from starter to switch, another cable from switch to negative connection of battery. Rubber boots not shown were installed on switch contacts. Open hood to access not a big deal.
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Not seeing where you activate the switch on/off. Your third photo appears to come up thru your floorboard.
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Old 07-30-2020, 05:31 AM   #21
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Default Re: Battery Isolator switch

Again, find and fix the draw !
If you have problems following the procedure let me know. I'll walk you thru it again.

I still recommend installing the switch where you want to put it.

Installing something in 'series' is just installing it 'in-line'.
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Old 07-30-2020, 06:21 AM   #22
Bruce of MN
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Default Re: Battery Isolator switch

Lots of previous threads on this. Search this forum for "disconnect kill cutoff"

two seaters and four seaters have different good spots for switches inside the cabin.
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Old 07-30-2020, 10:09 AM   #23
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Default Re: Battery Isolator switch

Quote:
Is the battery installed with a positive ground, as it should be?
Ditto
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Old 07-31-2020, 01:47 PM   #24
aquadave
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Default Re: Battery Isolator switch

Quote:
Originally Posted by Bill G View Post
Color of the wire is not important. Where the positive side of the battery connects to the frame, unhook and set aside that cable, and place one of the wires from the switch To the battery where the cable was, and connect the other switch wire to the frame. Now the switch is in series. Figuring out where to mount the switch is totally up to you and your preference. The cable you removed and set aside, you can toss it or save it. It is not used with the switch.
Thank you Bill. That's what I was looking for.
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Old 07-31-2020, 01:48 PM   #25
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Default Re: Battery Isolator switch

Quote:
Originally Posted by katy View Post
Ditto
Yes still 6 Volt Positive ground.
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Old 07-31-2020, 04:05 PM   #26
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Default Re: Battery Isolator switch

Redbird,
Sorry, didnít post the last pic showing the location in engine compartment under the floor board. Didnít want to cut the floor board or seat riser.
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Old 07-31-2020, 05:44 PM   #27
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Default Re: Battery Isolator switch

Basic electricity includes both series and parallel circuits but you really don't need to know everything about the differences unless you are designing a circuit of your own. The model A wiring harness and system is about the most simple set up a person can learn on with exception to say an 8N Ford tractor that even has less circuits. It is simple in the fact that the came with very few electrical components. This is a good link for diagrams.
https://www.mafca.com/downloads/Semi...ex%20Janke.pdf

The lighting system is the most complicated part since it all has to go through that big switch on the front side of the steering box which is kind of a bad place to put a switch but Ford kept it there till 1939. The head lamps have high and low beam circuits. There is a tail light circuit and a stop light circuit plus a park or cowl light circuit. Of all these, the brake light circuit is the most problematic for unknown current draw due to the funky switch that they had for 30 & 31. I'd start with that switch to find the current draw.

It's doubtful that the ignition system would be hot unless the ignition switch is defective. The ElectroLoc switches have been know to have problems after so many years in service.

The horn is not a likely problem area unless the wire inside the horn rod has bad insulation on it.

Most of the later model As have a vacuum wiper if it has a wiper at all and the instrument panel light isn't usually problematic due to it's simplicity but you never know. Most model As didn't have a dome light but they usually aren't problematic unless a rodent got to a wire somewhere.

This brings us back to the big diode in the cut out can for the generator. When you mentioned that it had more draw after it was replaced, that shouldn't be. I don't know what's up with that. I know that poor quality diodes can leak current through but I don't know what diode you have in there. Personally, I prefer the old electromagnetic cut out but a diode should work if it's a good one. It can be checked with a multi-meter on Ohms setting. It will have continuity one way but should have none the other way.

Last edited by rotorwrench; 07-31-2020 at 05:55 PM.
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Old 07-31-2020, 07:36 PM   #28
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Default Re: Battery Isolator switch

I would also agree that fixing the problem would be best. I recently worked on a Model A with this disconnect switch. There was so much corrosion/resistance in the contacts that it wouldn't let the full power of the battery to the starter. We bypassed the switch and everything was back to normal. Now the switch is removed.
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Old 08-01-2020, 10:24 AM   #29
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Default Re: Battery Isolator switch

You have a point there. A switch can be compromised by corrosion even if it originally was rated for the current load of the system. A 20 amp circuit breaker or switch can be used after the starter switch to isolate the battery. The 6-volt system needs the 1 AWG cable for power & ground to insure that the starter will function. A switch on the other side of the starter will still isolate the rest of system and a much smaller switch can be used. The starter likely pulls a lot more amps than anything else in the system. The battery can handle that but it needs those 1 gauge cables to be intact.

Last edited by rotorwrench; 08-06-2020 at 05:38 PM.
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Old 08-06-2020, 10:09 AM   #30
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Default Re: Battery Isolator switch

Thank you to all. Installation of switch went well. installed right at my feet, in front of driver's side of seat. Parasitic drain is something to do with the new cutout switch I installed on the generator. will have to get a new one.
I was able to cut two small openings in the floor board for the cables to the switch and the carpet covers these up so all you see is the switch. Fortunately or unfortunately being 6' 5" tall my feet won't hit the cables and wear at them. If my front seat was in the usual position the switch would be under the seat but I had to move the seat back so I could even drive the car.
Again everyone, thank you for your help.
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Old 08-06-2020, 12:02 PM   #31
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Default Re: Battery Isolator switch

If you're using a standard cutout [ non regulator] then try to get an original. Repo's are junk.
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