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I,ve wired the msd into the car(6 box)msd states to wire it direct to your battery,no problem,the bit i don,t like to much is that its hot all the time(not switched)whats the general concenus - have it hot 24/7 or switch it :: Thanks
 

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I was concerned about the same thing and NO fuse. :horror:

I wired mine (6-AL) according to the directions and no problems so far.
Have planes to add fuse when I get to rewiring under the hood, I’m still tuning and changing stuff now.

Will adding a fuse interfere with the MSD box?? ::
 

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It's my understanding that the box will not draw power until it gets a switched signal, i.e., from the ignition system when you turn the key. I had the same concerns as you, but a drag racing buddy explained it to me that way. I never have actually checked to see if it's true, but I haven't had any problems with it being wired the way MSD shows it.
 

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I wired that way also, as long as you don't hack the wiring and have any shorts, the thing will work perfect.
 

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The power supply to a spark amplifier is wired the same as a car stereo amplifier. There's a heavy gauge unswitched power supply wire and a light gauge switched "turn on" wire that's energized only when the ignition key is in the "on" position. The turn on circuit, when turned off, cuts off the power supply's path to ground. With no path to ground, no current is running through the power supply wire.

As long as the power supply has a path to ground, the engine will keep running. So if your engine stops running, you'll know that the turn on wire is dead and the power supply's path to ground is interrupted.
 

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Running a switch can also be a good anti-theft device ;)

And I dont believe it draws current the whole time. Its been a while since I spoke with the MSD techs and I believe they said it doesnt have a constant draw.
 

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I would NOT put a fuse on the heavy red wire.It could shut you down at a bad time. Like when you pull out in frount of a really BIG TRUCK !! :jawdrop: :horror:The red wire is big and heavy for a reason. MSD packs a punch and it needs a solid steady source of power.[IE battery]
 

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I would NOT put a fuse on the heavy red wire.It could shut you down at a bad time. Like when you pull out in frount of a really BIG TRUCK !! The red wire is big and heavy for a reason.
I disagree (politely, of course :lol:). The reason the wire is so big, is to allow enough current through it. Now if this wire were to get a break in the insulation, that much currently becomes a big problem, real fast.

I would much rather insure I don't have an electrical fire, since I'm not in the habbit of pulling out in front of big trucks. My main wire has ALWAYS been on a fuse or a circuit breaker. I ran it for a while with a 25 amp fuse, and now have it on a 30 amp self resetting circuit breaker (available at NAPA for about $5).

Been that way for 7 years now in my '66, and driven daily like that for all that time.
 
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