Dave Clark Posted November 16, 2020 Report Share Posted November 16, 2020 Bit of a random one, but my cooling fan pulses when I turn my ignition off.........even if eng temp is hot or cold. It stops when I arm the Clifford Alarm but I'm just curious if this is ECU related as it never happened on the standard ECU. Evo 6 Thanks in Advance Quote Link to comment Share on other sites More sharing options...
Adamw Posted November 17, 2020 Report Share Posted November 17, 2020 That sounds like a back feed. This happens when something connected to an aux output has constant 12V, rather than ignition switched 12V. Is it an evo plug-in ecu or a wire in ECU? Quote Link to comment Share on other sites More sharing options...
Dave Clark Posted November 17, 2020 Author Report Share Posted November 17, 2020 9 hours ago, Adamw said: That sounds like a back feed. This happens when something connected to an aux output has constant 12V, rather than ignition switched 12V. Is it an evo plug-in ecu or a wire in ECU? It's a plug in. Quote Link to comment Share on other sites More sharing options...
Adamw Posted November 17, 2020 Report Share Posted November 17, 2020 Ok, there must be something changed to do with the LO fan relay that is connected to pin 21 (aux 1). The power supply to this relay coil should turn off with the ignition switch (comes from pin IG2 on the ignition switch), so the fact yours still engages when the ignition is off suggests there is still power there. Possibly something to do with the alarm or imobaliser by the sounds of it. The high fan relay will have the same problem since it is powered from the same IG2 source, but that one wont backfeed as it is driven by an ignition drive rather than aux output (ignition drives dont back feed) Quote Link to comment Share on other sites More sharing options...
Dave Clark Posted November 17, 2020 Author Report Share Posted November 17, 2020 1 hour ago, Adamw said: Ok, there must be something changed to do with the LO fan relay that is connected to pin 21 (aux 1). The power supply to this relay coil should turn off with the ignition switch (comes from pin IG2 on the ignition switch), so the fact yours still engages when the ignition is off suggests there is still power there. Possibly something to do with the alarm or imobaliser by the sounds of it. The high fan relay will have the same problem since it is powered from the same IG2 source, but that one wont backfeed as it is driven by an ignition drive rather than aux output (ignition drives dont back feed) This is quite comprehensive thank you, however this pulsing never occurred until the LINK G4+ was fitted so there is either something that the LINK doesn't like, but as it's not a previous reported problem I'm guess there's a conflict between the LINK and the Clifford Alarm. It's the pulsing and not a constant supply seems odd though..........Time for an auto electrician I think Quote Link to comment Share on other sites More sharing options...
Adamw Posted November 18, 2020 Report Share Posted November 18, 2020 Yes, the fan output on the factory ecu was only ever designed to trigger a relay and nothing else - so it wont have any flyback diode etc. The aux outputs on a standalone ecu however need to be able to control anything from a VVT solenoid, a boost valve or idle valve, etc, some of which generate large flyback voltages. So the driver that a standalone ecu has on its aux output is a whole lot different than the factory ecu fan output, to protect it from these high voltages. It is this protection diode that provides a path for voltage to backfeed into the ECU when powered off. Since the factory ecu doesnt have flyback protection then it will still work with the relay powered incorrectly as there is no path to backfeed. The Link wont. The Link works fine with the factory wiring, but something has been changed on yours, probably un-intentionally as part of the alarm wiring. Pin 1 on that LO fan relay is what you need to fix. It should only be live when the ign is on. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.