Eddie Twadds

Struggling with a 171 SLK350. Main radiator cooling fan is on at 100% as soon as you switch on ignition. I had the main coolant temperature switch changed but no difference and all temps read OK. The aircon works OK and there is no code for Air Conditioning Condenser Pressure Sensor (pressure reads about 5.5 bar) which from Googling is a common fault which makes the fans run all the time.

There is a P0693 code - engine and AC electric fan suction fan output stage. The mechanic (non MB) reckons it is a cooling fan or fan ECM fault (engine cooling rather than aircon issue) but doesn't want to 'throw parts at it' - especially as the fan unit is expensive. Does anyone have any ideas where I can go from here?

Thanks

opinaca

Mine did that simply after installing a non OEM HID headlights system and custom Demon eyes.
Maybe an electrical interference of some sort.

Eddie Twadds

Not ruling anything out at the moment. Went through the connectors again last night but all seems good. Scratching my head on this one.

MBENZTECH

This is a common issue and is a defect of the engine control module. The engine control module is what tells the fan controller what percentage to operate the fan.