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Thread: Dual Cooling Fan Setup

  1. #1

    Default Dual Cooling Fan Setup

    I recently finished the Holley HP Terminator Stealth installation, and have been tying up loose ends before the spring temperatures arrive. I'm attempting to run two electric cooling fans with the Holley EFI running the fans. When the vehicle gets up to temperature only one fan comes on. I have checked power & ground to all connections, and at the relays. I also swapped relays with no change. Do I need to create a Custom Output in order to get both fans to operate under the one harness wire (gray/green wire)? Will I need to use an additional Input/Output wire from the main harness in order to obtain another ground configuration from the ECU pin?

    I'm using a Ron Francis Wiring AR-77 Dual Cooling Fan Sensor System that was on the car and working prior to the Holley EFI install. The Ron Francis setup uses one temp sensor to activate both relays via ground circuit. The Ron Francis system is wired so that both cooling fans come on at the same time. I wired the Ron Francis temp sensor wire to the gray/green Input/Output wire on the Holley EFI harness. I used the ground configuration for this wire and placed it in the J1-B3 ECU Pin. In System Parameters, I've checked both Fan #1 & Fan #2 check boxes. Electric Fan #2 is still in the Unassigned Output box when I access the I/O button on the toolbar, because I cannot place it in the J1-B3 ECU Pin due to the ground configuration being used by Fan #1. Does Fan #2 need to be assigned to a ground configuration in order to operate? The Ron Francis system is a single wire sensor wire, so I assumed that only one output wire would be needed. Additionally, both fans are 12" Mr. Gasket 1986 Electric Cooling Fans (1986 is the part number).

    I appreciate the work that everyone puts into this forum. It's a great resource and I contribute, a lot of the information on here to my early success with the Holley EFI. Thanks!

  2. #2
    Join Date
    Dec 2009
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    If Holley EFI is controlling you're electric cooling fans, then the "Electric Fan #1/#2" Outputs simply energizes the electric fan relay(s) at terminal #85 (ground) or #86 (+12V), depending on which Output Type you selected in Inputs/Outputs
    screen (System ICF).
    https://forums.holley.com/showthread...Fan-Holley-EFI (Wiring An Electric Cooling Fan - Holley EFI)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  3. #3

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    I also had a Ron Francis Dual Cooling Fan System before I installed my Terminator. Mine was adjustable but the fan relays work the same way. Sending a ground to the relay turns on the fan. Now it will be the Holley ECU that sends the ground to turn on each fan.

    First, the simple check. On your Holley Touchscreen, the menu that controls the fans is kinda buried. On the Touchscreen, select Tuning --> Basic --> System --> Outputs. That menu allows you to set both the start and stop temperatures for each fan. Check those temperature settings closely. Make sure the FAN 2 temps are not out of whack.

    On the Holley wiring harness, you should find a 3-pin connector labeled INPUTS/OUTPUTS. From the factory, the Gray with Black Stripe wire goes to the FAN 1 relay. The Gray with Green Strip goes to the FAN 2 relay. Both will provide a GROUND when the ECU wants that fan to turn on.

    These wires should be connected to the relays (one to each relay) where the Ron Francis GREEN Sensor wire used to go. Everything else should stay the same (except for taking out the Ron Francis sensor).

    Three tips:
    1) Make sure the ground wire coming from the fan is has a really good connection. If its poor, the fan will not run well.
    2) Stagger the “turn on” temperatures for the fans by 5-10 degrees so they don’t come on at exactly the same time.
    3) You can splice in a toggle switch to each of the Gray/Black and Gray/Green wires so you can manually turn on the fans if you want. Each toggle switch just has to supply a ground to turn its fan on.
    Last edited by 347Capri; 03-16-2018 at 11:14 PM.

  4. #4

    Default

    347Capri, thanks for the additional info. I spoke with a Ron Francis tech and I believe that I can wire both relay ground wires to the gray/green Input/Output wire on the Holley harness. Hopefully this works and I won’t have to use the additional Input/Output wire from the harness. I'll let you know what I find. Thanks again.

  5. #5
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    Have you considered PWM to turn the fans on. I used relays before I switched to PWM, and now I would never go back. One module runs both of my fans. The power draw is easier on the charging system. They never go above 65% DC. It dials the power up slowly, so there is no big power hit as the fans turn on. They engine temp is very consistent, no big swings in temp like you have with the fans turning on & off.

  6. #6

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    This is definitely an option in the future. I see that several on this forum have had great success with the Corvette fan module. At this time, I’m just trying to get the vehicle operational so that I can put miles on the system and allow the ‘Learn function’ to do its thing. Additionally, this winter has put a pretty good drain on the car's spending budget (ha ha), so since I already have the relays I will use them until I can make the switch to PWM. I like the ability to have control of the duty cycle with the PWM though. Thanks for the suggestion!

  7. #7

    Default

    My apologies for the late response, but I wanted to post an update. I'm currently using a dual relay setup to power the dual cooling fans (as described above). I wired the ground trigger wire on each relay to one of the Holley EFI output wires. So far I've had no problems, and both cooling fans operate as they should. Thanks for the assistance, this forum rocks.

  8. #8

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    Quote Originally Posted by 81 TransAm View Post
    Have you considered PWM to turn the fans on. I used relays before I switched to PWM, and now I would never go back. One module runs both of my fans. The power draw is easier on the charging system. They never go above 65% DC. It dials the power up slowly, so there is no big power hit as the fans turn on. They engine temp is very consistent, no big swings in temp like you have with the fans turning on & off.
    What PWM controller are you using?

  9. #9
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    Quote Originally Posted by LumbermanSVO View Post
    What PWM controller are you using?
    https://forums.holley.com/showthread...5386#post95386 (81 TransAm's Related Forum Post)
    https://forums.holley.com/showthread...9710#post99710 (81 TransAm's Related Forum Post)
    https://forums.holley.com/showthread...615#post100615 (81 TransAm's Related Forum Post)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

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