be careful on these fans and wiring, wiring them as on/off for full power through a 40A relay can cause the relay to weld itself on as the main fan sucks a ton of juice when starting.

MB drive these fans through a PWM control module to ease the amp draw.

You might want to use one of the standalone fan control units that have a probe which is stuck into the radiator fins to ease the fan on and off.

I installed a couple of fans in an old chevy truck and used three relays to run the fans in 2 speeds. the circuit simply makes the fans run in series or parallel.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)