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Master shut off with alt
#978449
04/22/11 11:51 PM
04/22/11 11:51 PM
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Joined: Aug 2009
Posts: 2,042
Mooresburg, Tn
'72CudaRacer
OP
top fuel
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OP
top fuel
Joined: Aug 2009
Posts: 2,042
Mooresburg, Tn
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 A few months ago,  someone posted a diagram of how to wire up a master battery cutoff when using a alternator,  and now I can't find it. Someone help a computer illiterate out please.  Thanks, Brian Dunnigan
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Re: Master shut off with alt
[Re: tboomer]
#978455
04/23/11 09:59 AM
04/23/11 09:59 AM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
Quote:
Quote:
If you want to do it the easiest way.... run the alt
output line back to the battery side of the master
exactly simple, and it would be protected..
I cant see any other way of running it on a race car
One thing about doing it this way it is NOT protected,
that wire is hot all the time... if you wanted to
protect at least part of it you would need to run a
relay as shown in the painless diagram... but if you
route it properly you wont have any problems... I've
had mine wired straight for 12+ years now
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Re: Master shut off with alt
[Re: 70AARcuda]
#978457
04/23/11 10:27 AM
04/23/11 10:27 AM
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Joined: Jan 2007
Posts: 7,664
IN
ahy
master
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master
Joined: Jan 2007
Posts: 7,664
IN
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Quote:
Quote:
If you want to do it the easiest way.... run the alt
output line back to the battery side of the master
x2..
did one today like that..
You just have to step up the wire size to prevent excessive voltage drop over the longer length. Size required depends on alternator amps and load... 6 guage would be a good place to start.
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Re: Master shut off with alt
[Re: sjs64polara]
#978460
04/23/11 10:40 AM
04/23/11 10:40 AM
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Joined: Nov 2003
Posts: 10,384
Upstate NY
Bigcube
I Live Here
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I Live Here
Joined: Nov 2003
Posts: 10,384
Upstate NY
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Quote:
Why do you guys run a hot lead to your alternator all the time or use a relay  Cant you just run the alternator line to the cold side of the master switch
What am I missing here
If you run the wire to the cold side of the switch when you turn off the switch the car will keep running because the alternator will provide the power.
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Re: Master shut off with alt
[Re: sjs64polara]
#978461
04/23/11 10:50 AM
04/23/11 10:50 AM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
Why do you guys run a hot lead to your alternator all the time or use a relay Cant you just run the alternator line to the cold side of the master switch
What am I missing here
You have to go to the battery side of the switch...
I run direct from the alt to the battery side with
a 100amp fuse near the battery
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Re: Master shut off with alt
[Re: Bigcube]
#978462
04/23/11 10:58 AM
04/23/11 10:58 AM
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Joined: Jan 2008
Posts: 449
Wisconsin
sjs64polara
mopar
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mopar
Joined: Jan 2008
Posts: 449
Wisconsin
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Quote:
Quote:
Why do you guys run a hot lead to your alternator all the time or use a relay Cant you just run the alternator line to the cold side of the master switch
What am I missing here
If you run the wire to the cold side of the switch when you turn off the switch the car will keep running because the alternator will provide the power.
Dumb me........I never thought of that, stupid stupid stupid.
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Re: Master shut off with alt
[Re: MR_P_BODY]
#978463
04/23/11 11:37 AM
04/23/11 11:37 AM
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Joined: Sep 2003
Posts: 6,847
Missouri
StrokerPost
master
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master
Joined: Sep 2003
Posts: 6,847
Missouri
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Quote:
Quote:
Quote:
Quote:
If you want to do it the easiest way.... run the alt
output line back to the battery side of the master
exactly simple, and it would be protected..
I cant see any other way of running it on a race car
One thing about doing it this way it is NOT protected,
that wire is hot all the time...
What I did on my Dad's car, because it would always be hot is put another Moroso master cut off up front low on the fenderwell so when he would need to work on it or remove the alt, he could just flip the switch so there wouldnt be a spark show. 
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Re: Master shut off with alt
[Re: moparniac]
#978465
04/23/11 03:41 PM
04/23/11 03:41 PM
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Joined: Dec 2003
Posts: 2,586
Illinois, Indiana, Louisiana
ProStDodge
master
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master
Joined: Dec 2003
Posts: 2,586
Illinois, Indiana, Louisiana
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As I see mentioned in a few posts above, if you are using or thinking of using a solenoid for connecting the alternator, do NOT use a ford style starter solenoid as it is not for continuous use. There are "continuous" duty relays available for under $35 which will work MUCH better. Here is an article I found better explaining the difference between standard starter solenoids and continuous solenoids. Quote:
Starter Solenoids and Continuous Duty Solenoids
Posted on April 04, 2011 in Featured, Technical
Check out this information on starter solenoid testing from Joe Glassford’s new book on vehicle testing procedures. This article gives you some much needed real world information on stater solenoid functionality that will help you better understand how to troubleshoot and diagnose problems later.
Starter Solenoid
Starter solenoid like the kind you see mounted on the fender well, or starter motor housing of some vehicles is used to bring current to a starter motor when the key is in the start position. This type is designed to pass as much as 400 amps.
The length of time this high current passes through a solenoid like this is limited. The limited time is the key to their usefulness. These solenoids use a coil with only 3 to 4 ohms of resistance. If this type solenoid was turned on and left on continuously, it would destroy itself from heat due to the amount of current passing through the coil winding. These solenoid windings pass close to 6 amps when operating.
Continuous duty solenoid
Continuous duty solenoid windings will draw less than 1 amp when operating. These solenoids will have approximately 30 ohms of resistance across the coil winding. This allows the coil to run much cooler allowing it to pass well over 100amps continuously without failure.
Never replace a continuous duty solenoid with a regular starter solenoid. The starter solenoid will burn out in a very short period of time if used for “continuous duty.”
Here is one I googled for under $20
Relay
There are also disconnect swithes available which have a second set of contacts for disconnecting power to an alternator relay.
Scott
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Re: Master shut off with alt
[Re: Bigcube]
#978468
04/23/11 06:10 PM
04/23/11 06:10 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
Who runs a mopar alternator?  Most folks opt for a one wire alternator of some sort be it powermaster or a GM one.
I run the Denso 3 wire ones... I dont care for the
1 wire alts... most of them have to have a few more
revs for them to kick in
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