Cooling fan problems

[tmelbye]

Hello World,
2011 Mercedes E 220 CDI /D 270.000 km.

Cooling fan runs continuously when car is turned off. Emptying battery.
This starts after turning of ignition, removing key and exiting vehicle. It takes about 20 seconds before there is a relay click and the fan starts.
This happens even when the car is cold.

Fan stops when connector on fan is removed but restarts when connector is put back.
Fan will also stop when ignition is turned on.

Whiles driving the fan operates as normal with speed of fan adjusting to temperature of coolant.

Gauge for coolant temperature functioning as normal.

I have checked all the fuses I can find and there is no visible damage to cables from rodents etc. Can’t see anything abnormal.

My thoughts:
There is power to the fan controller and also can-bus signal. Otherwise the fan would not work normal when the car is running and also stop when the ignition is on.

Temperature sensor should also be working as the gauge is working. If the sensor was malfunctioning the fan should not work as normal when driving, alternating speed depending on temperature.

My suspicion (but not sure if the parts work as I suspect)

Fault in fan controller (located in fan assembly). When not receiving signal from ECU it uses an internal temperature sensor that might be faulty and goes in to a failsafe mode to avoid motor from overheating after driving. (Residual heat keep heating up coolant) (not sure if that is how it works)

or...
Something wrong with the ECU sending the fan in to a failsafe mode to avoid overheating.
I was thinking about broken cable, but then it shouldn’t work when car is on and running.

Any thoughts on what could be failing so the fan goes bananas?
Is there anything I can check to find the broken parts?



A DIY solution suggested to me that I put some thought in to.

Cutting positive cable to fan controller. Putting in a relay that will close the connection when ignition is turned on. (could be any source as the relay doesn’t pull much power).

This will disconnect the power to the fan when ignition is turned off.
Problem with this solution is potential overheating after driving the car and residual heat from engine.

A DIY solution to the overheating problem would be to add a temperature sensor that closes connection when reaching a set temperature. Depending on temperature set on this sensor I should be able to connect this externally to the radiator or any coolant hose. Guess 80 C would be an OK temperature. I would then probably need to add a second relay to avoid power from going backwards to the point where I get power from ignition.

Hang with me (if even possible. I might repeat myself a few places.)

Original positive from cable going to fan controller split in two and connected to pin 30 on both relays.
Original cable going to fan controller connected to pin 87 on both relays.
Ground going to pin 85 on both relays.
Positive from battery (or other constant positive point) to temperature sensor (NO).
Out from temperature sensor to relay 1 pin 86.
Positive from ignition to relay 2 pin 86.

This should (if I’m not totally wrong) separate the two triggering signals so they won’t go backwards. (power from the temperature sensor will not go in to the cable from ignition point and giving me another headache.)

Any thoughts?
Am I way out in my thoughts of a DIY solution (last resort if nothing else works)

 

[onefortheroad]

How much is a new fan controller module ?

And could it also be something as daft as the switch ?

 

[mioba]

Not a fan of hacks and bodge jobs fo be fair.
Diagnose the fault, determine the fault and repair/replace the cause of the fault.

 

[mattkh]

............It takes about 20 seconds before there is a relay click and the fan starts.

You obviously can hear the click clearly.
I suggest you try to locate exactly which relay is this and report back.

 

[Wisswass]

Hi.
Got the same issue at my w212 OM605.
My fan starts to spin after the car is shut down.

Did any of you find a solutuon to fix the cooling fan?

 

[SL63 Mark]

My cooling fan always runs for a little while after the engine shuts down in hot weather. It then switches off after a while. This is perfectly normal, and is designed to provide adequate cooling when the engine is still hot.

 

[Wisswass]

My cooling fan always runs for a little while after the engine shuts down in hot weather. It then switches off after a while. This is perfectly normal, and is designed to provide adequate cooling when the engine is still hot.

That's normal if the temperature make it run, but mine go at full speed until the battery is drained.
Assume that is not normal.

 

[SL63 Mark]

That's normal if the temperature make it run, but mine go at full speed until the battery is drained.
Assume that is not normal.

Ah, no. Not good. Probably needs to go on Star for a diagnosis.

 

[supernoodle]

I would be looking at all the temp values possible in the diag tool. Fan control uses multiple inputs, not just coolant temp.
It's quite possible that a temp sensor is stuck in range so that it's not seen as high whilst in normal engine running but high for after run, so ends up requests cooling. If the temp is stuck the request will remain until the max after run timer is reached.

 

[Wisswass]

I would be looking at all the temp values possible in the diag tool. Fan control uses multiple inputs, not just coolant temp.
It's quite possible that a temp sensor is stuck in range so that it's not seen as high whilst in normal engine running but high for after run, so ends up requests cooling. If the temp is stuck the request will remain until the max after run timer is reached.

I know that the smart fan system use multiple inputs (like A/C, trasmission and so on), but it's really hard to find exactly wich one who is messing up the fan. . I've checked the temps, and noticed that the gauge is sometime responding different than the temp value at the live data on the diagnosic tool. Someone told me that there is two coolant temp sensors. So I have thoughts about the sensor who is connected to the gauge.
The live data coolant temp is always normal, but the gauge can rise alittlebit before it drops and a coolant service lamp is displayed in the display.
I can tell you that I've unplugged the connector to the cooling fan to avoid drain of the battery. That is the reason to that coolant warning sign in the display.

 

[sonic]

The wife SLC250d has a similar issue. Occasionally after about a 3 to 6 mile drive in light traffic the electric fan will run after the engine is switched off.
Come back after a longer run when the engine is at normal temp, it never comes on. In slow moving traffic the fan cuts in & out as it should do.
I have just left it as its not causing a problem

 

[Wisswass]

The wife SLC250d has a similar issue. Occasionally after about a 3 to 6 mile drive in light traffic the electric fan will run after the engine is switched off.
Come back after a longer run when the engine is at normal temp, it never comes on. In slow moving traffic the fan cuts in & out as it should do.
I have just left it as its not causing a problem

That's normal behaviour.
If your coolant temp/engine is hot
My fan starts and goes for full speed after ignition is shut off and the relay shut off the guidience head lights.
I can turn the ignition on (with cold engine) and off again, and the fan runs at full speed

 

[sonic]

It shouldn't come on after a short drive, it’s not quite up to normal operating temperature.
Yet when it is at normal operating temperatures & I switch off it doesn’t come on.