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Thread: Fan relay max amperage

  1. #1
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    Fan relay max amperage

    Hey guys,

    Been a while since I've posted here. I'm trying to find some concrete info that I haven't been able to dig up.

    Vehicle is '89 Lancer Shelby

    What is the max amperage draw I can safely achieve for the radiator fan relay circuit? I'm looking at aftermarket electric fans and need to know how many amps I can safely pull. Trying to get as much CFM as possible as I've moved to the high desert and am seeing engine temps a little above 220F on hotter days.

    This is the fan I'm looking at: M122K - Maradyne HP Fans

    https://www.summitracing.com/parts/mar-m122k#overview

    Thanks!
    -Zach

  2. #2
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Fan relay max amperage

    If you're serious about keeping the car cool, check out tryingbe on here. He details what it takes to keep a car cool with the ac on in AZ.

    As for the relay, the stock fans pull a lot of amps, so I wouldn't worry about 20 to 30 amps through it. At the same time, I would probably upgrade the wiring and relay anyway.

    - - - Updated - - -

    Eta: https://www.amazon.com/dp/B00BJLIB9G?tag=bravesoftwa04-20&linkCode=osi&th=1&psc=1&language=en_US

  3. #3
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    Re: Fan relay max amperage

    Thanks man! I'll definitely have to check around and see if he's written anything up. And if not just reach out directly.

    As for right now, I'm currently running the used-to-be-popular '92-'00 Honda aluminum rad replacement. Has a fan shroud, but still using the cheapo ebay fan that came with it. I don't have a shop where I live now so I'm hoping that a quality fan will compensate enough. If not.. we'll cross that bridge when we get there.

  4. #4
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    Re: Fan relay max amperage

    220F on street or freeway? What are you using to determine the coolant temperature?

    Factory calibration won't even turn fan on above 45mph until the temp is above 218F.
    https://www.thelostartof.net/tryingb...20schedule.jpg

    First, I wouldn't spend money until you determine what's lacking.

    Wire a manual fan switch and see you can get the temperature where you like it, this cost next to nothing and easy to do.

  5. #5
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    Re: Fan relay max amperage

    Thanks for your reply. I can see these temps climb and hang either around town or above 45mph, although most noticeable at freeway speeds. I have an Equus aftermarket temp gauge installed to monitor coolant temp. Running a FWD Performance stage 3 cal. I did look in my manual and yes stock calibration waits until about 220F to turn on the fan when traveling at speed. But with the stage 3 cal the fan is just on the whole time anyway at those temps and struggles to bring them back down. Even if idling for a while I don't seem to bleed enough heat to recover.

    I can tell that the engine doesn't like running that warm, however. Feels like it's pulling timing. When climbing hills temps will rise even more. I have found myself blasting the heater to compensate from time to time and that does help to control things.

    I don't mind spending the money to try a stronger fan, and through Amazon a return wouldn't be painful. It just doesn't seem that I have quite enough cooling efficiency to run at optimal temps.

  6. #6
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    Re: Fan relay max amperage

    Do you have working a/c?
    What your coolant capacity?
    Picture of the engine bay?

  7. #7
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    Re: Fan relay max amperage

    Not working AC, but hardware installed aside from compressor as it was an AC car. Coolant capacity close to stock. Will get picture soon.

  8. #8
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    Re: Fan relay max amperage


  9. #9
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    Re: Fan relay max amperage

    Link to an album of a my recent rebuild if interested. Block and head all gone through, everything cleaned. Shouldn't be any restriction to flow either.

    https://photos.app.goo.gl/gGdRGz9kbrTastqr9

  10. #10
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    Re: Fan relay max amperage

    I struggled with overheating for years as well. Getting everything around the radiator blocked off to stop air going around the radiator & forcing it through helped a bunch. What pushed the cooling system into the 'works damn fine' category was putting a Volvo S70 fan & 2-speed relay setup in it. That thing pulls some massive air through it; puts our stock units to shame on the low setting. I have the 2-speed relay set up so the ECU controls the high setting. The low setting is primarily controlled by a 195* temp switch in the outlet side of the radiator, which can be overridden by a switch on the bottom of the dashboard. I set the wiring up so it will all work automatically(I hate needing to babysit the temp gauge), but I can turn it on low whenever I want. My car doesn't have A/C in it yet, though it will when I can find the right condenser I want. I'm running a TU aluminum GLHS radiator in my Spirit R/T with a FMIC in front of it.
    “If the people of the nation understood our banking and monetary system, I believe there would be a revolution before tomorrow morning.” -Henry Ford

  11. #11
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    Re: Fan relay max amperage

    Quote Originally Posted by 86Shelby View Post
    I struggled with overheating for years as well. Getting everything around the radiator blocked off to stop air going around the radiator & forcing it through helped a bunch. What pushed the cooling system into the 'works damn fine' category was putting a Volvo S70 fan & 2-speed relay setup in it. That thing pulls some massive air through it; puts our stock units to shame on the low setting. I have the 2-speed relay set up so the ECU controls the high setting. The low setting is primarily controlled by a 195* temp switch in the outlet side of the radiator, which can be overridden by a switch on the bottom of the dashboard. I set the wiring up so it will all work automatically(I hate needing to babysit the temp gauge), but I can turn it on low whenever I want. My car doesn't have A/C in it yet, though it will when I can find the right condenser I want. I'm running a TU aluminum GLHS radiator in my Spirit R/T with a FMIC in front of it.
    Yeah I have one little spot to close off still, it's right between the intercooler and the radiator. Hard to see in the pictures of the engine bay I posted but it's there.

    However, before I make bigger changes I figured I'd just try a stronger fan since I already have the radiator and shroud in place. It's a universal 12" fan so it should just fit in place with what I already have. If that doesn't fix things then it's time to rethink the cooling system as a whole 🤷-♂️

  12. #12
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    Re: Fan relay max amperage

    Nothing stood out from the picture other than you don't have working a/c.

    I'm using a Volvo 850 fan in my GLH with custom shroud made from computer case panel. All gap is seal so air has only one way to go. Fan is set to on at 200F and off at 190F, fan is on when a/c is on. When I drive across the AZ to CA with a/c on, temp was at 206F steady.



    I tried an aftermarket fan, only thing it blew away was the money in my wallet.
    http://www.turbo-mopar.com/forums/sh...l=1#post935862


    Volvo 940/960 fan and shroud is almost a drop-in for my Daytona.
    http://www.turbo-mopar.com/forums/sh...l=1#post935940

    The fan is the same between 940/960/850/pre2000 S70/V70/C70, only thing different was the shroud.

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