Ground Disconnect?

[big-boss]

Why did the Kirkhams put the disconect on the negative side of the system- not the positive?

[xlr8or]

I dunno. I put mine on the hot side.

[CHANMADD]

Because when you disconnect the negative you don't get a "FAT" spark!!

[Maurice Johnson]

Electrical energy is created by the flow of electrons from the supply source (battery). Electrons are the negative charged particles of the atom. Disconnect the negative - stop the current flow. Shunts are installed on the negative side of a circuit to measure current flow. If you want a real brain cell exerciser, look up "alternate electron flow theory", or something similar.

[Dirty Harry]

When I built my car, I put the cutoff switch in the positive side. Now that I've thought it through a little better, I wish I would have put it in the negative cable. That's how I'll do it on my next car.

[Blu427]

Hello,

Nice an easy explanation is that you can easily short to the positive side of the battery side as the body & chassis are negative so isolation of the earth stops this happening. Just think the same as when you are using jump start leads the positive hits the body and sparks will fly!!

Cheers

[Morris]

Disconnect the positive side ...... and put the alternator feed on the disconnect switch ......on the battery side.....

If you disconnect the negative side .......the motor is spinning and the alternator will continue to have a output and seek a ground thru any other source.... or ground hooked to the motor......

So you won't be able to shut the motor off while it's running....... that is a must in all of the racing orgs.....

Morris

[big-boss]

Morris, So there is a race regulation that covers this? Thanks

[ng8264723]

For drag racing any cut of switch must cut complete power to the car and the motor. There is a nice sketch on how to correctly wire a disconnect switch at MADD electronics

[jimw427]

Oddly enough I just rewired mine last night. I have my cut off on the positive side, had the one wire alternator was wired to the non-battery side of the cut off switch. Turn it off, prevents it from starting, but while running, turn it off and we continue to run. Rewired it to the battery side of the cut off last night as the mightly electronic guros of this formum informed me and and what do you know it kills the engine now like it is suppose to and prevents it from starting. Don't know why it does, but it does, thats all that matters.

Thanks to all who helped and tried to explain this on several previous threads.

Jim

[RodgerH]

Originally Posted by ng8264723

For drag racing any cut of switch must cut complete power to the car and the motor. There is a nice sketch on how to correctly wire a disconnect switch at MADD electronics

Can you post the link to the sketch? Thanks.

[big-boss]

Sounds like I need to do some work on the wiring deal. My gut tells me it would be ok for a boat but not my bad azz chariot of fire that should be on the road tomarrow--- yes tomarrow. So now is not the time to reinvent the wheel, maybe next week. I am about to pis my pants with excitment as it is! I am sure you all know what I mean!

[maurice19]

Fire that baby up Boss, and enjoy
Maurice

[Ronbo]

Blu427 is right, with the neg disconnect it eliminates possible shorting of the "still hot" positive lead going to the switch and the vehicle body. Simalarly, when changing a battery it's important to disconnect the negative terminal first to eliminate a wrench slip shorting the positive terminal to the body.

Current is consistant across the circuit so the "spark" is the same regardless.

With either side disconnected the vehicle can still run, although the electrical system has now lost it's main filter (the battery) so electronic ignitions can malfunction and cause the motor to either shut down or run rough. Also some alternators will shut down with the battery disconnected.

[ng8264723]

Go to MADelectrical.com He has a wiring book for 7 dollars that has the diagram in it. It also has a bunch of other good ides. It's worth the 8 bucks
chris