Fraser Posted October 14, 2020 Report Share Posted October 14, 2020 I have my fan control wired from Aux 4 to a relay which is not on a switched live. Previously the fan was on a temp switch which prevented heat soak when the engine was off. When the ecu powers down the fan comes on. The fan works fine when the ecu is powered. Is there an output which doesnt pull-low when the ecu isnt powered? Im sure i read there is but i cant remember if i read it or made it up. It would be much easier to swap the pin than re-wire the factory harness. Thanks. Quote Link to comment Share on other sites More sharing options...
Gsab Posted October 14, 2020 Report Share Posted October 14, 2020 Its select able switching high or switching low. Remember not to exceed current limitation of the output should you switch high. A single automotive relay will be fine, draws about 50% of the outputs max. Quote Link to comment Share on other sites More sharing options...
Fraser Posted October 14, 2020 Author Report Share Posted October 14, 2020 Thanks for the reply Gsab. Yes, the polartiy is selectable but it is always pulled low when powered down. Swapping the polarity just inverts the action when the ecu is powered. Quote Link to comment Share on other sites More sharing options...
Yvo Posted October 14, 2020 Report Share Posted October 14, 2020 think you need an ignition switched positv to controle the relay Quote Link to comment Share on other sites More sharing options...
Gsab Posted October 14, 2020 Report Share Posted October 14, 2020 44 minutes ago, Fraser said: Thanks for the reply Gsab. Yes, the polarity is select able but it is always pulled low when powered down. Swapping the polarity just inverts the action when the ecu is powered. Had the same problem and simply gave an + Ve via my main relay. I have a single main relay making 6 other "hot" the moment the key is on. Perhaps Adam can advise on a different method. On my ViPEC instal I had 2x relays wired up working the fan. Quote Link to comment Share on other sites More sharing options...
Confused Posted October 17, 2020 Report Share Posted October 17, 2020 You will need to change your relay's coil feed to be ignition switched, rather than permanently powered. This way, the ECU will still pull to ground to activate, but when ignition is off, the coil cannot be energised, even with the ECU defaulting to grounding the outputs. Ben C 1 Quote Link to comment Share on other sites More sharing options...
Fraser Posted October 18, 2020 Author Report Share Posted October 18, 2020 Thanks for the replies. I know how i could fix it. I just wondered if there were any outputs which were open on power off rather than sunk to ground. Looks like there are not Quote Link to comment Share on other sites More sharing options...
Adamw Posted October 18, 2020 Report Share Posted October 18, 2020 On a Thunder, the ignition drives are the only ones that dont have flyback protection - so if you have a spare ignition drive these are the only ones that can be connected to devices that stay alive after the ECU is powered down. Quote Link to comment Share on other sites More sharing options...
Fraser Posted October 18, 2020 Author Report Share Posted October 18, 2020 Fantastic! Thanks Adam! Quote Link to comment Share on other sites More sharing options...
Fraser Posted October 18, 2020 Author Report Share Posted October 18, 2020 All fixed. Swapped the pins over to ign 5+6 and set to thermo fan 1+2 Thanks all! Quote Link to comment Share on other sites More sharing options...
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