Hi hi

While re-gassing my AC compressor today I've noticed that only the passenger side radiator fan will engage, either from AC cycle or from engine temp. My question to the gurus is what engages the drivers side fan? So far I've pulled the subfan relays out and all are fine, bridged the relay over and the fan starts, so not an issue with the fan itself, but simply have no idea what triggers the subfan relay. I'm thinking possibly ECU, but is it in series with the passenger side fan to only engage at excessive temperatures that I can't mimic while no load revving in my carport, or what?

Car is MY99 GC8 with ViPec ECU and no ghey mudflaps (may possibly be the issue).

Thanks, Alex.

PS: Tony, ideally all you can bring to this is a post count increase so please refrain from the pointless remarks that so often flow so freely from your keyboard.

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Air is for pussies.

different ecu's control the fans differently, some utilise both fans at once with variable speed (hi-lo), others will use 1 fan at full pelt & then kick the other one in if its not enough, sorry i cant remember which brand ecu do which, amybe check with whoever tuned it