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  • 1965 - 1973 Classic Mustangs -General/Talk-
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Is the (+) positive side of the coil a good 12 volt source?

  • Thread starter Thread starter BaLleRz68
  • Start date Start date Aug 27, 2007
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BaLleRz68

Founding Member
Oct 9, 2001
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Aug 27, 2007
#1
  • Aug 27, 2007
  • #1
Im wiring my electric fan soon and need a 12 volt/ignition source. Is the positive side of my MSD coil ok to use? Any thoughts are appreciated. Thanks.
 
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D.Hearne

New Member
Sep 29, 2000
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south louisiana
Aug 27, 2007
#2
  • Aug 27, 2007
  • #2
No, wire it to the battery directly. Fans draw too much power for them to share a terminal with something else.
 
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BlwnGazkit

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Nov 3, 2006
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Richmond, VA
Aug 27, 2007
#3
  • Aug 27, 2007
  • #3
The coil only receives 12 volts while cranking, the rest of the time it's powered through a resistance wire.

So, NO, the coil is a bad place for a voltage source.

What part of the fan are you trying to wire? A relay or the fan itself? The fan needs to be run through a relay to prevent overloading any of the factory wiring. It wasn't designed to handle that amperage.
 
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BaLleRz68

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Oct 9, 2001
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Aug 27, 2007
#4
  • Aug 27, 2007
  • #4
Thanks for the reply.I have the painless kit. Here is the link to the diagram.

http://www.painlessperformance.com/Manuals/30103Instruction.pdf

I need to find an "ignition/fan switch" source for the gray/white wire. I already spliced the ignition wire under the dash for my tach. Im just wondering if there is another source in the engine bay.
 

Tim65GT

Active Member
Feb 24, 2004
1,149
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39
West Texas
Aug 27, 2007
#5
  • Aug 27, 2007
  • #5
I need to find an "ignition/fan switch" source for the gray/white wire. I already spliced the ignition wire under the dash for my tach. Im just wondering if there is another source in the engine bay.
Click to expand...

Find a way through the firewall and attach it to the same ignition source as your tach. That would be best for your Fan relay operation.

The only other ignition source is to the + side of the coil, but it has the resistor wire in the path and is usually 6-9 Volts when running.
 

rbohm

Founding Member
Apr 12, 2002
6,698
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204
tucson,az
Aug 27, 2007
#6
  • Aug 27, 2007
  • #6
that wire is for power to the trigger side of the relay, thus you can wire it directly to the battery. that way the fan will shut off when the engine temp has dropped to where the ground is disconnected. or if you want, you can use the stator terminal as you 12v power source, like the factory does with the electric choke.
 

coupe5.0

Founding Member
Oct 31, 2000
117
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16
Aug 27, 2007
#7
  • Aug 27, 2007
  • #7
i wired mine into the alternator wiring, theres switched 12V there. Also used it to power the excitor wire on my 3G alternator conversion.
 
S

Soaring1

Banned
Jan 3, 2003
144
1
0
Texas
Aug 27, 2007
#8
  • Aug 27, 2007
  • #8
D.Hearne said:
No, wire it to the battery directly. Fans draw too much power for them to share a terminal with something else.
Click to expand...
Wrong. Electric fans need to be plugged into a fused block, and not the original fuse block that is 40 year old wiring. It also has to be a switched source for the 12V such as off of the ignition switch. Black with blue stripe if I remember correctly. If you hook that electric fan to the battery, it will run night and day. Not a real swift move.
 
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