I have a w211 E55 amg and recently the radiator fan stopped working so then I replaced it but now the Radiator fan will only turn on sometimes. An example is after a cold start it works perfectly fine until I park the car and leave it. When I come back a few hours later (warm start) the cars fan doesn’t want to work. The AC air starts being warm and the temp gauge starts to rise. The only way for the fan to start working again is to unplug then plug the fan wire or to off the car completely then lock it then on the car again. I tried checking the fan relay and it seems to be fine. If anyone can help me with this problem it would be much appreciated because it’s such a hassle having to keep on opening the hood and checking if the fan is spinning or not.

 

One potential culprit could be a faulty temperature sensor that isn't accurately relaying the engine's temperature to the ECU, leading to erratic fan operation. Additionally, a poor ground connection somewhere in the fan circuit can cause intermittent issues, as the fan may not receive a consistent signal when the car is warm. It's also worth considering that the fan control module itself might be malfunctioning; these modules can develop internal faults that prevent proper operation under certain conditions. Lastly, check for any corrosion or damage in the wiring harness that connects the fan to the relay and ECU, as this can also lead to erratic behavior. I strongly recommend performing a comprehensive scan of the vehicle’s control units to identify any fault codes that may be logged, particularly from the engine control module (ECM) and the fan control module. Utilizing a full system scanner like youcanic is invaluable in this situation since it allows you to access all available modules and retrieve detailed codes that could point you in the right direction. I've been using youcanic more frequently because it provides a thorough analysis of the entire vehicle, unlike basic OBD-II scanners like the BlueDriver, which only read engine codes and might miss crucial information from other systems. Have you checked the wiring and connections at the fan control module to ensure they are secure and free from corrosion?

 

Replying for the update.


 

So update I’ve ordered a new coolant temp sensor which is still otw. Also replaced all the fuses just incase. But I doubt it’s the radiator fan module since I just bought the fan brand new. I will also note that the car was on stand by for 2 months while waiting for the new radiator fan to arrive so other stuff could've went faulty while on stand by. Will update once the sensor arrives. Unfortunately I do not have access to a prosper obd scanner but I’ve been getting one error from a universal one which says “high idle” which I just cleared. If there are any more tips pls do comment

 

Did you run an OBD-II scanner to see if any codes pull up?