Alternator with a master kill switch

[rocetwildone]

I am installing an alternator this year and have a concern that my master kill switch that is mounted in the negitive battry calbe will not kill the motor?
I know on a street car if you remove the negitiave cable the car will continue to run.

[brad hibbard]

that is a really good question
and a great topic for safety meetings

I don't know the answer but will look into it with our friends at powermaster

I would say that i would just try it but we have lost MSD boxes on the dyno because of poor grounds and would hate to waste a box on a test that we can confirm by calling a pro

if you don't see me post something in the next few days its because I forgot about it----give me a call during the day and I will drop a dime to powermaster and get the facts

Brad
330-540-7223

https://www.race-1.com

[brad hibbard]

I spoke with a representative from Power Master today who told me when we run our Master Disconnect in the positive battery cable that the alternator wire needs to be hooked to the battery side of the switch.
That makes sense and easy to understand.

Then I asked what would happen if the Master Disconnect was used in the negative side of the system.
His initial response was that the engine would be killed upon disconnecting ....

Then I asked are you sure?

his response was not so confident----in fact he changed his answer and said the engine may actually try to run on

we are both confident that the engine would not operate perfectly but it "might" not shut down as we intend it to in an emergency situation.

here is my question---
why are people putting the disconnect on the negative side?

Brad

https://www.race-1.com

[ric78]

Brad talking about why people are putting the disconnect on the negative. That is the way the rule is written in the fastrack series. I don't agree with that and believe the master disconnect should kill the power supply not break the ground.

[brad hibbard]

Yikes!!!---that is a bit embarrassing
being part of the FASTRAK organization since nearly the beginning one would have thought I should know that

I just checked and you are absolutely correct---the 2017 FASTRAK rulebook states that the master disconnect is to be in the negative cable
It is written in red so that means it was new last year

I will certainly find out the reason for that specification and relay the alternator information to them.

I said in my first post on this thread that it's a great topic----guess I got that much correct---LOL

Brad

https://www.race-1.com

[brad hibbard]

many times this type of rule is transferred over from other late model series
before I contacted the southern folks I checked a few other rule books and see that Lucas Oil Series has the same rule---"disconnect must be in Negative cable"

It may take me a little longer than expected to get to the actual person that wrote this originally to see what their exact reason is for mandating the negative cable----I'm sure FT just copied the rule

Brad

https://www.race-1.com

[MLR19]

The reason I put the disconnect in the negative cable is , in the event of a crash that damages the sheet metal where the switch is located, it wont short out.

[brad hibbard]

That makes sense and goes with the mandated position on the decking
traditionally we put them in the drivers compartment where it should be secure from a shorting out situation

I think you have actually answered the question----we just need to be aware that when an alternator is used it might not shut down as expected

Brad

https://www.race-1.com