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E46 M54B25 Radiator fan override

EFI Wiring Fundamentals

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Hi Guys,

I have an E46 that i have removed the oem cooling fan setup and replaced with a spal 16' 12V 120W fan, i want to retain the setup where the car will trigger the fan itself and i just want to add a manual override.

attached below is a screenshot of the factory setup which has 3 wire connector, and the spal has 2 wire connector.

ps. I'm a complete newb to wiring so just bare that in mind if explaining. Thanks

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I don't know if it helps, certainly unlikely if it uses PWM, but what I've done in the past with conventional fans was to use on-off-on switches between the fan and the thermostat switch to give me a manual option for fans operated by thermostat switch, fans off, and fans operated by a manual over-ride. The manual terminal being to a fused battery feed* or ground, depending on the way the fan is wired.

So it's one terminal to the 'stat, middle terminal to fan, other terminal power for manual - amend for ground path.

NOTE, the fans draw a fair bit of current, and can flatten a battery quite quickly if it's under-charged, or small.

*I did it this way so the fan ran with engine off, to lower radiator and under-bonnet (hood) temp's. Another option may be to take a relay feed from the acc' position of the ignition switch so removing the key prevents accidentally leaving the fan running.

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