Cooling Fan High Speed Relay BEC melted

Discussion in '2005+ Mustang GT 4.6L Tech' started by mineralgoogt, Oct 5, 2013.

  1. one eyed willy

    one eyed willy Pizzle fo shizzle

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    Do you know if the ecu puts out a ground or 12v to trigger the fan? Have you tried disconnecting the wire from the ecu and triggering it? If you did this and the fan worked then you could rule out everything else.
     
  2. olds350

    olds350 forum member

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    well, of all things.... I had a hand held tuner I bought used w/ the car. Someone on another forum suggested just trying it just to test. Installed a 89 tune and set the low fan speed to 180. I'll be damned if it doesn't work. The stock tune will not turn on the fan, the custom tune will.

    Why?

    At least now I don't have to buy a new PCM. I have no clue why this is working now. Guess I'd have to get the original PCM flashed. I'm glad this works, but I'm not sure why it works. Reset the low and high speed fans to 190 and 210, so I'm good for now.

    If anyone has a clue as to why the stock tune doesn't work and the custom tune does, I'd appreciate some insight...
     
  3. irishpwr46

    irishpwr46 Official Site Vandal

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    Apparently this is my newest issue. can someone tell me the exact wire that i need to use to power on the low speed relay? i saw green/violet speculated before but i just want to confirm
     
    Last edited: May 15, 2015
  4. irishpwr46

    irishpwr46 Official Site Vandal

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    what wire am i hooking up to 86

    [​IMG]
     
  5. irishpwr46

    irishpwr46 Official Site Vandal

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    anyone?
     
  6. lito

    lito forum member

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    Checked the BEC and is actually melted? Block connector and BEC pins that is
     
  7. irishpwr46

    irishpwr46 Official Site Vandal

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    yeah it was in real bad shape. i ended up running the relay and getting it to come on with the high speed, i turned the temp down on the high speed in the tune so it would come on. im going to look into a more efficient fan though since i have the slim one that comes with the paxton kit and it is still running up around 212 with the ac on
     
  8. 46addict

    46addict 13726548

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    Does anyone know the answer to this? I'm having the same problem with the high speed not turning on after driving for a while. I suppose I could wire up a simple 3-way toggle switch but having a temperature reference from the PCM would be nice.

    I'd love to know how TexasBlownV8 got the LEDs set up as well. That seems to be the best solution if there is no programmed reference from the PCM.
     
  9. 46addict

    46addict 13726548

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    Re-read the thread and found the answer. I suppose pin9 C2 from the PCM would go to pin 86 on the relay, and ground the pin 85.

    [​IMG]
     
  10. Detka

    Detka Junior Member

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    Same my issue any update? 2009 gt
     
  11. JeremyH

    JeremyH 3V Fuel Guru S197 Team Member

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    Huh?
     
  12. ChewyR

    ChewyR forum member

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    I had this issue, and after looking at the Ford wiring diagram I gave up on the idea of an auxiliary relay. I dremeled the melted connection out, and soldered 10 ga jumper wire to the pin directly. Then hooked my jumper wire back into the harness. So far so good.
     
    Last edited: Nov 1, 2017
    JeremyH likes this.
  13. 46addict

    46addict 13726548

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    I bought this car from mitch and I'm checking in to say the new box melted again and made the fan stop working after about 10 minutes of operation. My solution was to install a manual switch & relay and a temperature reference on the upper radiator hose to monitor temps. I'm not selling this car so I didn't feel bad about drilling into the panel and losing automatic fan control.
     

    Attached Files:

    Last edited: Nov 6, 2017
  14. Detka

    Detka Junior Member

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    Till now im suffering
     
  15. Morereps

    Morereps Junior Member

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    Hello everyone and great information. I’m having the same issues so i opened my BEC to find two burned terminals. I was thinking of doing the external relays but the write up link someone shared on how to do the wiring doesn’t work anymore. Could someone please share that information again? This will be greatly appreciated.
     
  16. Moparkansas

    Moparkansas Junior Member

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    I'm currently fighting this battle. Can anyone tell me for sure does the trigger wire provide the ground or does it provide the power to trigger the relay? I found a green violet wire in the corner of the wire loom in the BEC that is closest to the fire wall and pulled it out of the connector but I can't seem to get it to trigger the relay with the A/C on. How do I tell for sure which wire it is and can anyone tell me for sure does the trigger wire provide the ground or does it provide the power to trigger the relay?
     
  17. Ramrod512

    Ramrod512 Junior Member

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    Im getting this issue too. Replaced the whole fan assembly and it worked for a whole hour then i started to have issues when the temp increased and with the fan and a/c staying on. When i checked the fuse box i could hear clicking from the relays and see the fan trying to turn on and the a/c clutch trying to engage. I also smelled a slight burning smell coming from the engine bay. Like something plastic melting or electrical burning. I havent pulled the BEC yet but reading everyones posts im going to do that next.
     
  18. bl817

    bl817 Member

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  19. If understanding the diagram is hard for some people to comprehend, they need to take it to someone that can comprehend and just pay them to do it. wiring in relays is about as simple as wiring gets. I seperated my entire circuit from the car and used the 2 (lo & hi) ground signals to trigger my external 40 amp relays. 10 years and not one issue. no fucking switches or probes or sensors necessary.
     
    OUTLAWPHOTOGUY likes this.
  20. OUTLAWPHOTOGUY

    OUTLAWPHOTOGUY Junior Member

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    I am battling this now with my wife's car, factory block under the fuse block has melted connections to high and low speed relays, put in an aftermarket fan controller but it only lasted a bout 2 weeks, ordered a Derale PWM controller and that should work with the GT500 fan. Can you send pics of what you did and a description of what wires you connected to?
     
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