Thread: Master power switch. Electrical GURUS needed

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Originally Posted by Itoldyouso

Do-able and should I do-able are two different things. It is do-able to jump off a cliff, but......................................

Sometimes you just do things the way they are customarily done because others have found out that is the right way to do them. Put it on the positive side and you will sleep better at night.

Don

No one is jumping off any cliffs! The guy wants to control the flow of electricity. With a switch he can open or close the circuit. It won't matter if it's on the positive or the negative side. The electron flow won't care as long as the circuit is complete with good clean connections! Don't believe it? Go to any car and lift off the negative terminal. Of course we all know the car won't start, won't crank, it just does NOTHING! Just what this guy wants. And just cause that's not how you think it's "customarily done" doesn't mean it's unsafe or bad. You aren't the know all / end all in the automotive field! I remember the days of positive ground systems, still work on a few of them too. And we all sleep well at night too! Sorry if this seems short or ill tempered, you're response implies something less than desireable.

I left my pile of bricks outside so I can't throw them at anyone

My rule of thumb, as decreed by something I read a few years ago(plus my own idea for safety) - if it is a standard, non electronic car, either negative or positive will do fine. If it's a newer car or has lots of electronics, the best way to disconnect is via the positive side. I do the positive side regardless plus my car - it has a fair amount of electronics, i.e.full MSD ignition and all of my gauges. And yes, I do have a separate 50 amp maxi-fused 10awg line to an individually fused module for those items I don't want to shut off with the master switch which so far, it's the stereo(5 amps) and the trunk lift(10 amps) with the solenoid operated doors to eventually follow - (maybe).

Originally Posted by 34_40

No one is jumping off any cliffs! The guy wants to control the flow of electricity. With a switch he can open or close the circuit. It won't matter if it's on the positive or the negative side. The electron flow won't care as long as the circuit is complete with good clean connections! Don't believe it? Go to any car and lift off the negative terminal. Of course we all know the car won't start, won't crank, it just does NOTHING! Just what this guy wants. And just cause that's not how you think it's "customarily done" doesn't mean it's unsafe or bad. You aren't the know all / end all in the automotive field! I remember the days of positive ground systems, still work on a few of them too. And we all sleep well at night too! Sorry if this seems short or ill tempered, you're response implies something less than desireable.

Geesh, didn't you see the smiley faces? My point was that while you are doing something like this it takes no more effort or money to do it the RIGHT way. Would it work by interupting the negative side? Sure, but the problem is that you still have the entire positive side unprotected and the potential is there, albeit slim, that it could short out against something metal and cause a problem.

Where I work we have to operate under strict guidelines by the American Boat and Yacht Council (ABYC) they mandate how and where every component of a boat is placed and installed. Again, I realize this is a car, but the principles are the same........both have engines and batteries. The Council insists the switch be on the positive side, for the reason I mentioned above. I have never seen any disconnect switch installed on the negative side and have been in this industry for over 20 years.

Sorry you took offense for some reason to another opinion, but when we give advice on any forum we need to present the best way to do things, not just one that would get by, and if I had to chose between you getting irked and him having an electrical fire, guess which one wins out?

Don

Denny, thanks for clearing that up!

IC2, no bricks are needed! We're all good here!

ITYS!, I did see you're smiley but even after reading it again, I don't see any opinion offered. I would like to note that I offered an apology in case I read that wrong. It doesn't matter really I guess, the guy asked a question and we all offered our "opinions"...

We all have our reasons I guess and choosing to do things a certain way because we think it's best goes with the turf. I does make my blood boil when a "new idea" is squashed because "we never did it that way".. If we all drove the same car with red rims and wide whitewalls, life would be terribly boring!

It's Saturday! It's raining It's time to head to the garage!

It's Saturday! It's raining It's time to head to the garage![/QUOTE]


Yep, me too, I have an engine to build. As they say, opinions are like.........................

Take care, hope it stops raining. Wish it would pour here to cool it down a little.

Don

No roof, but I am working fully protected in all ways . I'll be nice and dry working under the truck today.

Don

Denny, that's just wrong in so many ways!

If there is a switch between the negative battery post and ground and it is turned off there is not a live positive wire anywhere on the vehicle that will arc if you touch it to metal because negative is disconnected from ground and therefore, ground metal is dead and cannot be used to complete a circuit.

denny there a stem sticking out of that guys heads .that must mean he is done??? and yes the hot is only hot when you have a ground

Originally Posted by DennyW

That stem is there, so when your under water, you can open it, and light it for a light to see with... But, if you don't use belt weights, you will float to the top...

And yes, unhook either the pos or neg from the battery, and everything is dead...

WELL OK
i now i was thinking this was some new sex suit deal were they throw a coat of wax on you and toss you down a flight of stairs

Originally Posted by AzDon

If there is a switch between the negative battery post and ground and it is turned off there is not a live positive wire anywhere on the vehicle that will arc if you touch it to metal because negative is disconnected from ground and therefore, ground metal is dead and cannot be used to complete a circuit.

Exactly! The first thing any manual tells you before starting most work on a vehicle is. remove the ground (negative) cable from the battery. It makes sense to me that my switch wired this way, will function as I desire it to.

Now my engine is EFI, has a computer, and electric fuel pump, so I'm thinking that in an emergency situation, IE; smoke, fire, sparks, or accident, I should turn off the ignition switch, then turn off the battery switch. Engine is off, Fuel pump is off, any shorts will stop immediately.. makes sense to me. Oh and perhaps I should add grab fire extinguisher..lol

Denny, now see what you started...

Originally Posted by Chev malibu

Exactly! The first thing any manual tells you before starting most work on a vehicle is. remove the ground (negative) cable from the battery. It makes sense to me that my switch wired this way, will function as I desire it to.
That's because of the potential spark that could ignite battery fumes if you remove the positive cable first.


Now my engine is EFI, has a computer, and electric fuel pump, so I'm thinking that in an emergency situation, IE; smoke, fire, sparks, or accident, I should turn off the ignition switch, then turn off the battery switch. Engine is off, Fuel pump is off, any shorts will stop immediately.. makes sense to me. Oh and perhaps I should add grab fire extinguisher..lol
Not necessarily so, any capacitance in the circuit could fuel the fire until it is totally discharged.
Denny, now see what you started...

And the NHRA rulebook states that a battery disconnect will interrupt the positive side per techinspector1

Originally Posted by DennyW

Just look at all the fun we just had though.

It WAS a "lively" ... discussion! Wasn't it?

It has always been an unwritten rule when working around batteries to disconnect the negative FIRST! The reason for that is, should your wrench touch the body, you won't have a spark when you touch the grounded metal and possibly cause the battery gases to explode.
(when I was in vocational high our teachers would insist that we place a folded shop towel over the positive terminal to further prevent any possible connection of positive & negative! It's a practice I still use!)

I don't believe it has anything to do with your switch manufacturer intending anyone to insert the switch into that side of the circuit.

Everyone is correct tho' in the most common and some sanctioning bodies rules is to require the Positive side to be interupted with the switch.

Originally Posted by DennyW

I think...the rules apply due to the rear mount location of the battery in the rules. That would be the closest point to the trunk mounted battery. How ever, VW, and a few other vehicles had under the seat mounted batteries...
Also in those rules for racing, they say you must also have a manual ignition off switch too, besides the disconnect switch. The disconnect switch in that case is for the track members to be able to disconnect power in case something goes way wrong... That's in case any Hot wires are pinched, causing a short, and spark if fuel is leaking.

Denny is right on the money here. As far as the old Beetles, that's the one exception that I can think of where we have to allow a battery in the driver's compartment without it being in a sealed steel, aluminum or approved poly box and vented to atmosphere if the car is stock. Once the electrical system is modified or the stock rear seat bottom cushion is removed for drag racing, it falls under the sealed box rule. Technically, with the battery still in the stock location under the rear seat cushion even though the cushion isn't there any more, a sealed box will suffice and no master cutoff is necessary on the rear of the car until the car reaches 9.99 E.T. or 135 MPH in the quarter mile.

Originally Posted by techinspector1

Technically, with the battery still in the stock location under the rear seat cushion even though the cushion isn't there any more, a sealed box will suffice and no master cutoff is necessary on the rear of the car until the car reaches 9.99 E.T. or 135 MPH in the quarter mile.

As to no master cutoff necessary, does this only apply to the VW, as to the ET/mph, or any car that runs slower then that? I'm sure there is some class, maybe street class (?)that runs without external cut off switches. Least I have never noticed them on the cars. They race, then drive home in them..If I ever take the Cobra to a strip, I hope I'd be in that class, and still drive it home after..

So would the manual "ignition off switch" that Denny mentions include the keyed ignition switch, after all that's manual?