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  •  » 12v ign source for fans and msd

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    12/17/2022 9:21 PM  #1

    1fststang
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    12v ign source for fans and msd

    I need a 12v ign source for my msd.  On the driverside apron i have a 12v ign source from my AWW harness for my fans.  I plan to connect both 12v ign feeds or my fans.  Would it be to much to hook my msd box to this as well ?

    I don't have another 12v ign source on that side of the car and not wanting to run extra wires if i don't have to.

    Both the fans and msd are wired directly to the battery so the 12v ign on only sends 12 volts to basically trigger the fans and msd when in run.

    i have a large 12v ign feed on the passener side and can extend and use it if necessary.

     

     

    12/18/2022 10:18 AM  #2

    Mach1Driver
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    Re: 12v ign source for fans and msd

    We can't really answer that without knowing the year, and if it has a tach and alternator warning light, or an ammeter? Most likely you will need to attach the coil of a 12v relay to starter solenoid terminal "I", then use the switching contacts of the relay to control the loads. It will be on when the key is in start or the ON position. Since you already have a source on the passenger side, it would be easiest to extend that to the drivers side.
     

     

    12/18/2022 1:16 PM  #3

    BobE
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    Re: 12v ign source for fans and msd

    In addition to info needed is the model MSD box you have and the radiator fans you're using.  
    Note that the fans have wiring direct from the battery, there is likely already a relay to provide control of the fans.  

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

    12/18/2022 2:39 PM  #4

    1fststang
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    Re: 12v ign source for fans and msd

    Car is a 67 Fastback.  I'm in process of installing an AWW harness.

    I have a set of dual taurus fans with a Spal controller with Spal relay for the second fan.  This set up has power directly from batter but need a 12v ign on to trigger the relays.  My AWW harness has a 12v ign on specifically for electric fans.  I'm using this lead for the fans.  

    My MSD is a 6Al and i have it mounted on passenger side near radiator support.  I have wiring to the battery for both 12v and Grd.  The msd has a small gauge wire that needs 12v ign on to signal the box when the engine is in crank or run mode.

    I think I'm just going to run the large gauge wire in the AWW harness that's for ign feed for coil
     

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    12/19/2022 10:36 AM  #5

    BobE
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    Re: 12v ign source for fans and msd

    I believe both the fan controller and the MSD box only need a signal, that doesn’t draw a lot of power, to operate.  As such, the I think the system will run just fine without going to the larger wire.  A call to the tech support at MSD and Spal would confirm this.
     
    Make sure this ‘ignition’ feed is providing 12v and not a ‘resistor’ feed that reduces the voltage to the coil.

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

    12/19/2022 1:55 PM  #6

    Raymond_B
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    Re: 12v ign source for fans and msd

    If it is just a 12v "signal" for key on it won't carry very much current. I can't imagine there'd be any issues doing so. Be sure to mount that fan controller somewhere that gets some airflow and allows it to cool off, it will for sure generate a lot of heat PWM'ng those fans.

     

    12/19/2022 8:26 PM  #7

    1fststang
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    Re: 12v ign source for fans and msd

    looking thought the msd installation manual and here is what they describe.

     This wire is responsible for turning the MSD On and Off. Connects to a switched 12 volt source such as the ignition key or switch. (Max current draw of .250 mA.)

    That means that wire only pulls .00025 amps.

    Now reading this I have to believe connecting the msd box to the same 12v ign signal as the fans should be fine.  

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    12/19/2022 10:37 PM  #8

    Rudi
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    Re: 12v ign source for fans and msd

    250 milliamperes = .25 amps

    250 micro amps =  .00025 amps

    Good work ain't cheap, Cheap work ain't good!   Simple Man
     

    12/20/2022 11:59 AM  #9

    BobE
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    Re: 12v ign source for fans and msd

    Rudi wrote:

    250 milliamperes = .25 amps

    250 micro amps = .00025 amps

    Rudi – correct … even at 0.25 amps, one wouldn’t need a heavier wire size.

     

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

    12/20/2022 6:16 PM  #10

    1fststang
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    Re: 12v ign source for fans and msd

    I'd like to install some plugs at the msd so i can easily disconnect if i need to.

    Is there any problem installing a deutsch connector or weatherpack for both wires that run to the coil, tach, 12v ign on/signal?  

    would be nice to just have 1 or two plugs at the msd box for easy removal if engine comes out or msd box need to come out.

     

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    12/20/2022 7:51 PM  #11

    Bullet Bob
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    Re: 12v ign source for fans and msd

    Good, sealed Weatherpack or Delphi connectors should be fine.  Not a lot of current in those circuits to deal with.

    "you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
     

    12/21/2022 5:24 PM  #12

    Raymond_B
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    Re: 12v ign source for fans and msd

    1fststang wrote:

    I'd like to install some plugs at the msd so i can easily disconnect if i need to.

    Is there any problem installing a deutsch connector or weatherpack for both wires that run to the coil, tach, 12v ign on/signal?  

    would be nice to just have 1 or two plugs at the msd box for easy removal if engine comes out or msd box need to come out.

     

    My 1st preference would be Deutsch, then Metripaks over Weatherpaks due to size. No problem with adding the plugs, matter of fact it makes perfect sense for servicing.
     

     

    1/05/2023 6:10 AM  #13

    1fststang
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    Re: 12v ign source for fans and msd

    I installed a deutsch connector at the MSD 6AL box.  Have everything connected to harness and coil except the 12v ignition on lead to the msd box.  I decided to use the larger pink coil + wire from the AWW Harness.

    My problem now is the deutsch connector pins and sockets i used were for 14-18 gauge wire like the wire coming out of the msd box.  The pink wire appears to be 12awg so i can't use the same connector.

    Options i have are
    -use a butt connector that reduces the 12awg to 18 awg just ahead of the connector.
    -Use a terminal strip near the msd on the fender apron where i can connect the heavy 12v wire on one side and other leads that need 12v ign on   
    -go back to tie the msd 12v ign on in to the lead in the AWW harness meant for the electric fans.  this lead would need to support both fans and msd
    -pull another lead from ign switch or other 12v ign on source to run to msd

    I want a clean and functional install and I know I'm probably overthinking but wanted to run past you guys and see what you have done or suggest.

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    1/06/2023 6:36 AM  #14

    wsinsle
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    Re: 12v ign source for fans and msd

    I don't think the fan wire is an option, probably not made up in the start position which the MSD would need.

    If this forum can't fix it, it isn't broke.
     

    1/06/2023 11:05 AM  #15

    BobE
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    Re: 12v ign source for fans and msd

    1fststang wrote:

    I installed a deutsch connector at the MSD 6AL box.  Have everything connected to harness and coil except the 12v ignition on lead to the msd box.  I decided to use the larger pink coil + wire from the AWW Harness.
    .

    Before using the pink wire, verify that it isn't the OEM replacement resistor wire (that was also pink) that drops the voltage down to about 9v. The MSD box will not operate at that voltage. 
     

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

    1/06/2023 5:25 PM  #16

    1fststang
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    Re: 12v ign source for fans and msd

    I'm using the AWW harness.  The instructions with the AWW harness says you can use this as a 12v ign power for ignition box or for power to a distributor

    i just need to reduce down the 12 gauge wire to fit the deutsch connector and smaller wire going in to the msd box.

    i have a butt connector that will take 14 gauge down to 18 gauge.  MY pink wire is 12 gauge but still fits in the connector all though snug.  I may use that to take the pink 12g wire down to 18g to go in to connector.  this wire only give 12v ign on signal to msd box.  the actual power is from a heavy wire directly to the battery.

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    1/07/2023 9:26 AM  #17

    Raymond_B
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    Re: 12v ign source for fans and msd

    1fststang wrote:

    I'm using the AWW harness.  The instructions with the AWW harness says you can use this as a 12v ign power for ignition box or for power to a distributor

    i just need to reduce down the 12 gauge wire to fit the deutsch connector and smaller wire going in to the msd box.

    i have a butt connector that will take 14 gauge down to 18 gauge.  MY pink wire is 12 gauge but still fits in the connector all though snug.  I may use that to take the pink 12g wire down to 18g to go in to connector.  this wire only give 12v ign on signal to msd box.  the actual power is from a heavy wire directly to the battery.

    Rather than add a lot of connectors/reducers you can simply cut some of the strands reducing the wire diameter to fit the pin. 
     

     

    1/07/2023 6:48 PM  #18

    Bolted to Floor
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    Re: 12v ign source for fans and msd

    I don’t know that you’re over thinking it. Sounds like you want a clean functional installation and that’s a good thing. If that 12 gauge wire is the one that pulls the .25 amps then I have 2 suggestions.

    If you have wire strippers with holes for sizes, then use the #14 hole to strip the #12 wire. Get a good bite on the wire then roll it 90 degrees and do it agin. That should cut some of the outer strands and let it slide into the smaller connector.
    The other option is to go googling for the metal inserts for 12 gauge wire that fits in the connector. I did that for some weather packs.

    John  -- 67 Mustang Coupe 390 5 speed
     

     

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