BlackBird_SR71 Posted March 1, 2021 Report Share Posted March 1, 2021 Atom G4+ ave Coolant fans triggered by Auxiliary Output #2 ( Pin #20) . Works fine controlled by ECU. Would like to add an Manual Override switch which would simply ground the #85 Terminal on the Fan Control Relay. As this is also connected to Pin #20 on ECU, are there any special precautions that have to be made. Such as adding a Diode to wiring to ECU to prevent any type of Feedback. Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 1, 2021 Report Share Posted March 1, 2021 You cant have a relay that is live all the time connected to an aux output as it will cause a backfeed. So if you are intending to use this override switch when the ignition is off the only way to do it would be to move the fan relay to an ignition drive. Quote Link to comment Share on other sites More sharing options...
BlackBird_SR71 Posted March 1, 2021 Author Report Share Posted March 1, 2021 This would be only for turning on the Fan while the engine is running. Usefull in some Racing situations such as sitting waiting on starting line before a Hillclimb or Autocross. Or just as a general Override . But I was thinking ( in my Sleep ) . I should be able to do this with a Generic input. Use Grounding Toggle switch on spare Auxiliary Input to actuate Aux #2 output to fan relay. Hmm I could use the AC quicker function as well. Is that Voltage triggered or sink to ground triggered. I think I just answered my own question. Now back to bed... Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 1, 2021 Report Share Posted March 1, 2021 If that is the case then your original suggestion of your switch grounding relay pin 85 is fine. The other option is connect the switch to a DI and use a virtual aux & GP output for the fan function. Quote Link to comment Share on other sites More sharing options...
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