I subscribe to a monthly newsletter email from The Hot Rod Co. In this month's email is featured a batt. disconnect from Flaming River Co. As I've heard of several modified cars catching fire due to some wire or cable shorting out when the car was unattended, I've been cosidering such a switch on my roadster. So I took a look @ the newsletter feature and also sent a question to THRC about it. He sent back a pdf of the literature from FR and it also breaks the alternator circuit at the same time. Further states that this is required in some NHRA cl***es for cars running an alternator. This switch is a good deal more expensive than some others of the same ampacity, but without the alternator circuit feature. I went to FR website and got very little additional info. Can/will someone explain to me the reason for this additional feature? Dave
So that it is also a shutoff switch. On serious drag cars the switch is mounted so that it is accessible from the outside of the car and turning it off will kill the car. (With an alternator the car can keep running if all you do is cut off the battery.) So unless you're going racing or need to be able to shut down your car from behind while it's running you do not need that feature.
a regular shutoff switch doesnt shut the alt output off when the car is running. if you had an electrical short that wouldnt let you shut the engine off the alt would continue to supply current to the electrical system [and also the source of the problem] if you just want a safety when the car is not running a regular shut off switch will do.
I bought the one one Speedway sells and there's just two posts on the back of it. I put the wire from my one wire alternator on the hot side (from the battery) I turned the switch to the off position and tried to start the car, it didn't work so I thought I had it installed correctly. One day I parked the car and tried to kill it with the switch but it stayed running. It was feeding back through the alternator. I switched the alternator wire to the other post (from the switch to the starter.) It won't start with the switch in the off position, and it kills the car when it's running plus the charging system is running correctly so I think that's how it goes. It's a good idea, I had them in my circle track cars and it's right on my dash in easy reach during an "oh ****" moment.
You can also get these switches from a Caterpillar heavy equipment dealer, they feature a nice small steel key that's removable when it's in the off position.
Never used a cutoff. Everything I have and had was newly wired by me. ****y at***ude to say the least... Two weeks ago went for a Sunday drive one evening with my wife.. pulled into the garage and locked it up. Was farting around the yard for ten minutes and suddenly for some reason got the idea of opening the garage back up to take a peak at the engine. When i arrived in the garage there was no smoke or smell anywhere. I opened the hood to find the generator smoking! Right away I thought the regulator screwed up and was overcharging it when the engine was running. Thinking it was cooling down I decided to throw an air gun on it to cool it quicker. It got hotter! blowing sparks out of it.. Five minutes p***ed so I decided to take the generator off the car before it caught on fire.. I found after removing the hot wire it was alive giving the thing juice. I unhooked the battery and measured it with a temp gun at 300 degrees! Here the regulator contact stuck giving the generator juice. I am so lucky the dear Lord was watching me that day. It would have burnt all the cars and the garage down. Needless to say i installed cutoffs on everything and use em!
Thanks for all the quick replies! After reviewing your answers and giving it some thought, here's my take on the issue: My battery is gonna be in the trunk with a 1/0 welding cable to the front, and it sure wouldn't hurt to have a cutoff in the trunk, both for safety and a theft retardant, especially with the trunk locked. But as a cutoff for the alternator to prevent "run on", I wouldn't want to have to run the alternator wire all the way to the back of the car in order to use the same switch! The logical place for that wire is up front and as short as possible. Seems to me I could, if desired, put a switch up front to handle that deal. I know it wouldn't meet NHRA requirements, but so ****ing what! My roadster would never ever meet their rules anyhow and will only get on the strip @ Nostalgia Drags where they sort of look the other way as long as you don't get TOO fast. A fenderless Hiboy falls into Altered cl*** in NHRA rules and no way will my car ever have that sort of roll cage, etc. So I think I'll put a single pole switch on the positive batt. cable, mount it in the trunk, and be done with it! Dave
Electrical circuits in cars should have some type of protection so that if something goes wrong the cars do not catch fire. They make fuses that go up to 500A and can be used in cars. When I install wiring in a vehicle I add an inline fuse to where if there is a problem with something downstream like a defective master on/off battery switch or pinched wire a fuse will blow. I would rather replace an inexpensive fuse and not a whole car. Jim
I would think that a battery disconnect from the negativeside, and a cicuit breaker on the alternator side would do just fine
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