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Diode Location

Discussion in 'FAST Support Forum' started by 33Dan33, Sep 20, 2017.

  1. 33Dan33

    33Dan33 New Member

    Joined:
    Jan 8, 2015
    Quite some time ago there was a thread here that addressed this topic, and I was hoping somebody could answer it again for me. I have a 16" spal fan connected to my xfi 2.0 box and have it set to come on and turn off at specified temperatures. I also added a toggle switch into the circuit in order to have the ability to manually control the fan if I ever wanted to. Somebody here had mentioned that this might not be a good idea because turning on the fan manually could send a spike to the xfi box, and that a diode could be added to keep this spike from reaching the box. If this is the case, can somebody please tell me where in the circuit this diode should be located and what type of diode etc. should be used? Any help would be appreciated, thanks! Just looking to prevent anything potentially harmful from happening..
     
  2. gtsman

    gtsman Member

    Joined:
    May 30, 2014
  3. 33Dan33

    33Dan33 New Member

    Joined:
    Jan 8, 2015
    Okay thanks, I'll take a look at the link you posted. Nice car, love those old Mopars; ragtops even more.
     
  4. Fastmanefi

    Fastmanefi Active Member

    Joined:
    Jun 4, 2011
    Location:
    Sonora, CA
    You must be using a relay to control the fan motor - you cannot drive the fan without it. The XFI only provides a ground signal for the relay coil, so there is no inductive spike. All you need to do is add your switch from the same relay coil connection that the XFI is controlling to ground.
     
  5. 33Dan33

    33Dan33 New Member

    Joined:
    Jan 8, 2015
    Thanks Fastman. You are correct, I do have the spal relay installed that controls the fan motor. The relay wire that would normally be connected to the temperature sensor that comes with the kit is instead connected to both the xfi box and the toggle switch as well. Glad to know then that there's no spike involved.
     

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