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Key OFF, fan ON...

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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Hi Guys,

I am having a silly issue with the cooling fan on my Micra....

- Car and wiring are completely stock and everything runs fine on the OEM ECU

- I 've installed an PnP Haltech Elite 1500, using the 64-pin nissan adaptor (for S13, S14, S15, N14 Sr20s and my humble CG13 K11)

The fan generally operates as it should BUT it switches ON, when the ignition switch is completely off (car-key-in-pocket-Off, not just engine off). I would understand some kind of "heat soak" delay with the power still on, but this is not the case here, since the engine is running below the fan threshold when switching off.

Any hints?


hi epameinonda. nice to see you and meet you here. did you check the fan settings?

Hi Antreas, nice to meet you too.

I got a reply from Haltech support. The Haltech PnP adapter connects a DBW output instead of a DPO to the fan relay. The DBW outputs are grounded when the ECU if turned off, and because the FAN relay has constant power, the fan starts.

I have to either re-wire the relay, or swap the DBW output to a DPO on the harness patch and this should solve the problem.

sounds like your relay for your fan the 85 pin is being triggered by your ecu (low side triggered) and the 86 pin is being given high side power from a constant source. there are two simple options to alleviate the problem you are having. basically when the power is cut from the ecu I believe its dumping all its outputs to ground, hence powering up your fan. so either you trigger your radiator relay from a high side output from your ecu to the 86 pin on the relay and then ground your 85 pin on the relay. or you can keep the ecu low side triggering the relay but instead of having constant power to the 86 pin you can use the same switched power or enabled power that your ecu is being powered by to trigger the 86 pin on your relay. I myself got hung up on this very problem when I purchased a leash electronics relay board that I ordered to have low side triggered I found out afterwards that all the 86 pins on the relay were simply connected to the 30 pin (constant battery) then when I turned off my ecu (key switch back then) all the loads would power up. I have since threw the leash electronics relay 12 board on the shelf and have built my own unit using GEP stuff

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