Battery switch placement

[ivoryjohn]

I took a battery back today that had gone bad because I had cycled it one too many times by letting a small draw run the battery down to zero. My fault but I trusted the warranty would save me and I abused the battery through my neglect. The warrant didn't save me and I was disappointed to learn my year warranty expired six months ago. Ninety bucks down the drain. Expensive lesson.

There was a battery disconnect on the positive pole of the battery but it was one of the cheap ones that you have to unscrew the knob on the battery every time under the floor board and because it is inconvenient I didn't always use it except when I was going to let the car sit for a few days or weeks. Or I just forgot.

There are a number of post about battery switch placement on the firewall, on the seat frame and under the hood on the starter. There are pros and cons but i[B]s there a technical reason for which side of the battery, positive or negative that is preferable?[/]

My fog lights and turn signals are hooked up to the negative battery terminal. If I mount the new switch I ordered today on it's bracket off the starter I am afraid I will fail to use it just as I did the cheapo switch I have now. Besides I would have to mount the wires for the turn signals and fog lights outside between the switch and starter or they would still be in the live circuit. I like them tucked hidden under the floor boards out of sight.

The ideal site for the switch, as I see it, is on the positive side of the battery, under the seat with the wires inside the tool box, and the on-off lever sticking out through the seat frame on the driver's side. It would be fairly convenient, hidden and safe, I would think, if I wanted to kill the battery because of engine problems.

Does it matter where you put the switch....positive or negative?

[Mitch//pa]

i like it under the seat , convienent and would hate to open the hood everytime, plus its hidden and a cleaner job than hanging it on the starter..
I installed a disconnect in case my starter switch sticks or other emergency

[Jim/GA]

Originally Posted by ivoryjohn

Does it matter where you put the switch....positive or negative?

No.

[BudP]

I do as Mitch did. I put my battery disconnect on the seat frame under the driver for my A with cables under the seat. It's half-hidden, not very noticeable, and the first thing I turn on when I get in the car and the last thing I turn off when leaving the car. It's part of my routine, and couldn't be easier.

[ScottNW/Ohio]

Originally Posted by Mitch//pa

i like it under the seat , convienent and would hate to open the hood everytime, plus its hidden and a cleaner job than hanging it on the starter..

I agree, mine is under the seat
Make it easy to get to quickly (just in case something goes wrong)
Nobody even knows I have one, unless they see me flip it

[Jim Parker Toronto]

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I have two of the heavy duty type, one in car.They are both within reach from the drivers seat. It took a bit of extra wiring and had to drill a few holes, but I feel it was worth it. Don't by a cheap switch. I don't think which terminal you use is important, as either one will isolate the battery.

[MikeK]

1) It's not a matter of + or -, it's which is the ground/earth connection. That is the battery lead you need to disconnect to avoid danger of shorts even with the disconnect switched off. If you disconnect the "hot" lead, you can still short anything touching the frame to the battery terminal. With the switch in the ground lead, everything from BOTH battery terminals is dead to the frame. That is why all repair manuals caution to disconnect the groung lead first, not the "hot" when doing work.

2) A simple two terminal (SPST) disconnect switch WILL NOT kill a running engine. The gen/alt will continue to power the ignition. To kill the engine as well, you need a DPST (four-terminal) switch. The heavy terminals disconnect the battery, the smaller terminals are best connected into the ignition/coil circuit or the generator output. The smaller switch is too light for a fully loaded alternator. If you wish to disconnect a high amp alternator output you need a heavier four terminal disconnect switch.
For Ignition or 20A gen or alt + 500A Battery: (~$25)

For alternators up to 300A + 1000A Battery: (~$75)

I like my switches mounted through the center crossmember, with an access hole in the floorboard. Just lift up the corner of the mat or rug to flip the switch.

[Kurt in NJ]

Why don't you fix the draw??

[sethkestenbaum]

I went the MikeK route and was happy that I did. - Seth

[matt92vr4]

Def need to put the switch on the ground side.

[bbrocksr]

Originally Posted by Jim/TX

No.

Yes it matters, Put it in the ground cable. On the floor by the drivers seat.
If you have an electrical problem and the wiring is smoking while driving you can reach down and turn off the battery switch. Also when the starter switch sticks just shut the battery off.
Just like having Insurance, Hope you'll never need it but its nice to have when you do.
Bill

[Jazzjr]

I run 12 Volt Neg Ground, with a alternator, off and on switch in Seat Riser.
Neg battery post cable to Switch, other side of switch to Transmission Bolt, than ground strap from Clutch Housing to Frame. #10 white wire is ground wire to Fuse Box ground block. No other wire comes off Neg Battery Post, when switch is off, No Power anywhere, I always put in Off position every time I shut off Engine.

[Paul in Colorado]

Originally Posted by MikeK

1) It's not a matter of + or -, it's which is the ground/earth connection. That is the battery lead you need to disconnect to avoid danger of shorts even with the disconnect switched off. If you disconnect the "hot" lead, you can still short anything touching the frame to the battery terminal. With the switch in the ground lead, everything from BOTH battery terminals is dead to the frame. That is why all repair manuals caution to disconnect the groung lead first, not the "hot" when doing work.

2) A simple two terminal (SPST) disconnect switch WILL NOT kill a running engine. The gen/alt will continue to power the ignition. To kill the engine as well, you need a DPST (four-terminal) switch. The heavy terminals disconnect the battery, the smaller terminals are best connected into the ignition/coil circuit or the generator output. The smaller switch is too light for a fully loaded alternator. If you wish to disconnect a high amp alternator output you need a heavier four terminal disconnect switch.
For Ignition or 20A gen or alt + 500A Battery: (~$25)

For alternators up to 300A + 1000A Battery: (~$75)

I like my switches mounted through the center crossmember, with an access hole in the floorboard. Just lift up the corner of the mat or rug to flip the switch.

Mike,

Why do you have a battery cable coming up through the floorboard, instead of making the connections under the floor? Also, what gauge and length cables did you use, and where did you get them?

Paul

[MBI Houston]

Paul, can you please explain how you attached the switch to the crossmember?
Thanks.

[Paul in Colorado]

Originally Posted by MBI Houston

Paul, can you please explain how you attached the switch to the crossmember?
Thanks.

Mike is the one to ask, not me. He answered my questions in a personal message. Maybe he will respond to your question.

Paul

[James G.]

About 15 years and 40K miles ago I mounted my cutoff switch in in my 1931 Tudor in the floorboard near the driver right side seat post. All cables are under the floor. The switch is in the negative (hot) cable. I don't buy the argument about + or - and something going to chassis ground. Once the hot terminal is isolated you can ground anything you want without a problem. Just keep one post isolated which the switch does.

[Hotrodmyk]

Originally Posted by MikeK

1) It's not a matter of + or -, it's which is the ground/earth connection. That is the battery lead you need to disconnect to avoid danger of shorts even with the disconnect switched off. If you disconnect the "hot" lead, you can still short anything touching the frame to the battery terminal. With the switch in the ground lead, everything from BOTH battery terminals is dead to the frame. That is why all repair manuals caution to disconnect the groung lead first, not the "hot" when doing work.

2) A simple two terminal (SPST) disconnect switch WILL NOT kill a running engine. The gen/alt will continue to power the ignition. To kill the engine as well, you need a DPST (four-terminal) switch. The heavy terminals disconnect the battery, the smaller terminals are best connected into the ignition/coil circuit or the generator output. The smaller switch is too light for a fully loaded alternator. If you wish to disconnect a high amp alternator output you need a heavier four terminal disconnect switch.
For Ignition or 20A gen or alt + 500A Battery: (~$25)

For alternators up to 300A + 1000A Battery: (~$75)

I like my switches mounted through the center crossmember, with an access hole in the floorboard. Just lift up the corner of the mat or rug to flip the switch.

OK, I recently purchased a DPST switch. The instructions say to install it in the "HOT" side battery cable. I know all manufactures say to disconnect the ground cable before performing certain jobs. Why do you think they say to put switch in the hot side? Below is a similar switch.

[Tom Wesenberg]

" Why do you think they say to put switch in the hot side? Below is a similar switch. "

Becuse of the second small terminal used to connect to the alternator.
Otherwise I'd switch the ground side.

[MikeK]

Put the disconnect in the battery-to-frame ground path. Use the two smaller terminals to switch the 'hot' feed to the ignition circuit, not as a gen/alt output disconnect. When the disconnect is off all points to frame-ground will be safely dead as intended and the engine will also stop as there will be no power to the ignition from either the battery or the spinning gen/alt.

On a stock A, the short black lead from the terminal box to the coil is the 'hot' path you need to interrupt with the two smaller cutoff switch terminals, not the red lead from the coil to the popout switch. If you have electronic ignition you interrupt the 'hot' feed to the non-popout ignition switch, not the wire from the switch to the electronics.

[jmeckel]

Opening up the frame or "ground" side is ok as long as you make sure that NOTHING has been "grouned" to the battery side of the switch or hooked direct to the battery. Hooking to the battery is a trick some do with 2-way radios (including cb's) to try and reduce noise. If this is done, and you for example forget to turn the master switch on and step on the starter you will "let the smoke out of the radio" and we all know once you let the smoke out of electronics, you can never put it back in! This happens because the high current draw will try to use the small wires that are hooked to the battery or battery side of the switch as the return path to the battery, and it will smoke the wires and the equipment... Trust me I have seen many customers do this on construction equipment and it is never good!