Electrical Disconnect Switch

[Richard Cope]

Would like to get advice on an electrical question.  I have a 39 Plymouth, 6 volt - positive ground with the battery under the seat.  Want to install a heavy gauge disconnect switch in the floor that would break the circuit at the battery.  Thus when the car is not being used, will be easy to disconnect all of the electric.  My concern is, should the switch be connected to the positive or negative battery cable.  Thank you in advance for your help.

 

Regards,

Richard

 

[Plymouthy Adams]

your call, basically whatever will be easier for you....either breaks the circuit...that is the intended use of the switch....

[Richard Cope]

Great,  Thanks for the help.  Positive will be easier.

Quote

 

 

[DonaldSmith]

I've used disconnect cable clamps on my battery.  I usually undo the ground (+) connection when I won't be driving the car for a while.  Back off the knob, and pull the cable awy from the post clamp.

For a while, I had a second battery to provide 12 volts (another story). The second battery has the same clamps.  I can switch batteries in a hurry, if I ever have to. 

 

[BobT-47P15]

I use a switch like this.....however, my battery is under the hood and I mounted this switch thru a hole in my

firewall, so i can operate it from the driver's seat.  There might be a place under your seat for such an item.

These switches have gotten kind of hard to find......think I googled "battery cutoff switch" to find one.  They

cost more than those cable end items, but I personally like it better.  I purchased a short additional cable to

put that switch in my system.   I think Cole Hersee Co. makes one like this....stock no. 75903.

 

 

Edited July 2, 2018 by BobT-47P15

[Jakub]

They should be easy to buy in any tractor - parts store, I think that any tractor uses them. If no, It's required by law (at least here, but it should be simillar in US) for any motor boat to have it - so marine shop it's the next place to stop by.

I have one in Packard 120, also battery under the seat. I mounted it on the seat frame; but REALLY IMPORTANT is the proper wiring. By "proper" I mean really, really thick - thickest You can find. If it would be too thin, the car wouldn't start when the engine is hot - the starter would engage and start cranking the engine, but there won't be any spark. I had that problem in my Packard, even thought about converting it to 12V, but welder - wire was the solution. 

[BobT-47P15]

My cables on the P15 are 00 gauge, made up for me at a battery supply store.  You should be able to use 0 gauge OK i think.

 

I used to find the switches like mine at swap meets.....but the last 3 or 4 years the vendors have not had any of them.

So I began looking on the internet and found the type I wanted.  Seems like it was about $28 or so.  

 

[desoto1939]

In our club a person had the cutoff switch mounted on the floor of his 1936 plymouth and then one day while on tour the engine stop running and he could not get the car started.  Because the cutoff switch was on the floor his foot hit the switch by accident when moving his feet around and he turned off the power from the battery.  So make sure if you mount on the floor board that you will not hit the switch with your foot.

 

for better battery life you should also think about keeping a trickle charge on the battery.  This keeps the battery yup to par and then also prolongs the life of the battery. Having a bettery sit and then only getting charged when the engine is runn causes the plates to slowly loose the metal and then the battery discharges.  This has been discussed at the AACA annual meeting in Philadelphia and by keeping it charged you should get 6+ years out of a battery and maybe even more.

Rich Hartung

Desoto1939@aol.com

Edited July 3, 2018 by desoto1939

[Richard Cope]

Thank everyone for your suggestions, got the switch in - a time saver.  Getting to the battery in the 39 takes a little effort, bottom seat has to be removed, then the battery cover.  Installed the switch on the floor, just back of the front edge of the seat.  When the seat is in, hardly noticeable.  Cleaned all of the terminals and put a connection on the battery so that a trickle charger can be connected from outside the car.  The battery is a good distance from the starter, haven't had any issues however considering a adding a second Optium battery in parallel as a insurance for evening car shows.  The current battery is sitting in an old 6 volt wet cell that I gutted, if I remove the old battery case will be plenty of room.. 

Once again thanks for the help

Scan0001.pdf

 

Rich

[DrDoctor]

   Ron Francis Wire Works has that type of disconnect switch, as does Mac’s Antique Auto Parts (a division of Ecklers), and Danchuck (tri-five chevy parts). I also checked with my local auto parts store, and he had one, and keeps it in regular inventory.

[dodgeguy]

Put it in ground side , which ever way you are running i.e. pos ground or neg ground. When installed in ground side the battery is taken completely out of the circuit. say you drop a wrench it wont short out or if installed in trunk and some thing slides over to hot side wont spark. I struggled with this for years, actually installed one wrong in trunk of hot rod ( hot side) and had it short out. All and I do mean all modern service manuals say disconnect neg side of batt before work and they are referring to ground side. My 2 cents worth.

[1949 Wraith]

On 7/2/2018 at 7:00 PM, BobT-47P15 said:

My cables on the P15 are 00 gauge, made up for me at a battery supply store.  You should be able to use 0 gauge OK i think.

 

I used to find the switches like mine at swap meets.....but the last 3 or 4 years the vendors have not had any of them.

So I began looking on the internet and found the type I wanted.  Seems like it was about $28 or so.  

 

I install these switches an all my cars. Install high on the firewall out of sight, if the battery is in the engine compartment. In front on the floor of the drivers seat covered by the floor mat if the battery is under drivers seat. So far the grandkids haven't figured out why nothing works when they are horsing around in the vehicles.

 

These are readily available on E-Bay for around $12-15

 

https://www.ebay.com/itm/NEW-Master-Battery-Disconnect-Switch-kill-2post-SPST-kill-cut-off-nascar-ON-OFF/292137545245?rt=nc&_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D52473%26meid%3Dcaeddcb3b6104fa29192a718eb6a7288%26pid%3D100005%26rk%3D5%26rkt%3D12%26mehot%3Dag%26sd%3D123049864971%26itm%3D292137545245&_trksid=p2047675.c100005.m1851