The Stovebolt Site Forums The Shop Area The Electrical Bay Master Cut-Off Switch

Put a heavy duty switch in my 49 years ago. Each time I put the truck in the garage I turn it off. I have mine running through the Positive cable off the battery.
My neighbour has a POS 74 Land Cruiser and has something draining his battery. I suggested a trace. Instead he bought a cut-off switch and said he is going to install it on the Negative cable. I asked why and he said that the truck has two 24V batteries, one for accessories and the other to start it.
I looked online about which terminal/cable should be attached to the switch. Most said POS but a few said NEG with valid reasons. Typical Google answer I guess!

I recently installed a cut off switch in my ‘52 3100 and did the same research thru Google you mentioned. I decided to switch the negative, reasoning that I didn’t want 12 volts positive under-the passengers seat. on the pros side, it was easier to access the negative terminal for my setup.There’s pros and cons either way.

If you're installing the switch near the the battery, install it on the chassis ground side. For most folks that will be the negative side, though there are some (GMC) positive ground systems out there. The only reason I could see for installing the switch on the hot side would be if the switch was installed in a location where the ground strap was not practically accessible.

My thought is it doesn't really matter which side you put it on. You're stopping the flow of juice either way. To me the best way is the easiest/shortest wire from the battery. That being said in the case of my Cobra replica that I built I needed to have a keep alive wire for the engine computer and radio memory's so I had to put the switch in the pos side with a small (5?) amp fused circuit around the switch going to just those two items. If any kind of short were to happen in that the fuse would blow quickly.

Good point regarding electronics requiring constant voltage; I hadn't thought of that. Not an issue on my 49. I'm in the middle of an engine swap and alternator conversion right now. I'm going with a master cutoff that clamps onto the negative battery post. Under $10 on AMAZON. I'm also mounting a 50 amp manual reset circuit breaker on the firewall, where the regulator was removed, between the battery and the ammeter to protect the under dash wiring and ammeter. It's pretty much impossible to find an alternator under 50 amps nowadays. The breaker can be tripped manually to serve the same purpose as a positive side master switch. If I ever do add something requiring constant voltage I can wire it to battery side of the breaker. When I want to swing wrenches without worrying about arcs-n-sparks I can twist the switch on the battery post.

Mine is installed on the negative side. I have it mounted under the seat with key for it facing out for access. Been that way for about 6 years and no problems.

I had mine on the positive side in BillyBob and I started building up a collection of Delotron alternators with burnt out diodes. I moved it to the ground side and I haven't damaged an alternator since.

Interesting comments. On my 53 I had it on the POS side with the switch under the seat within reach. On my current 49 it is again on the POS side and has been that way for years. I guess both sides are good.
Thanks