I have a 2004 CLK 320. The engine cooling fan is not coming in. I checked the fuse it is good. Any suggestions? Relays?

Thanks

 

The fuses are F32 in front pre-fusebox and F51 in front SAM, though this does several functions including instrument cluster.

Control is via the main engine ECU.

The fan does have its own controller, which may be faulty

If you can, check voltages on 4 pin plug to fan.
Pin 1 ground
Pin 2 12V from fuse F32 in pre-fusebox
Pin 3 12V from F51 in front SAM
Pin 4 12V control from ECU

 

Can you tell me the location of the pins. I see the plug. I have 12V there. Both fuses are good. The fan spins freely. Where and what am I looking for as far as the fan controller?

Thanks

 

Fan controller is part of the fan.


The wire from the ECU (pin 4) is a modulating signal, which controls the fan speed. With a multi-meter you will probably see a variable voltage, higher voltage the faster the fan should run.

Best way to check is with a good mercedes diagnostic scanner, which can output the signal to run the fan. Altrnatively connect 12V to it and it should run at full speed.
Numbers are usually moulded onto the plugs.

 

Very good. Thank You. I will check the wires. I appreciate it. 👍

 

I haven't had a chance to do anymore checking until now. Looks like thermostat is good. It opens. Seems like the coolant is not circulating. Would this whatever it is cause that problem? I am not sure what this is or it's function. Any help would be greatly appreciated. Top radiator hose heats up fine as does the bottom of the motor hose that runs into this whatever it is. I was thinking this may control the circulation of the coolant?

 

I figured out that that is an auxiliary water pump. Could that be the cause or should I look to replace the main pump? Seems to me that the coolant doesn't circulate. I am not sure if this auxiliary pump could keep that from happening. The reason I ask is because warm/hot coolant goes into the auxiliary pump but it never flows. Is there a valve there that isn't opening? The only two hoses that get warm are the top radiator hose and the small one going into the auxiliary pump. Thanks for any help and knowledge. 👍

 

Anyone?...
Anyone?...

 

Kind of surprises me that there is no input on this.

 

The auxilary pump has no valves. It is just a pump.

It normally runs after turning engine off, and you press the "rest" button, to keep warmth in the car when parked.

I am not sure if it runs when driving though.

They are prone to failing. You can test it by connecting 12V to the two terminals and you should hear it run.

I doubt this will be the cause of our issues, as it only has a small flow.

Do you have an overheating issue?

Have you flushed the radiator. If you have high miles, then changing water pump is always a good idea, along with belt and idler pullys, and give it a good flush at the same time.

 

Do I have overheating issues? Yes. I am very hip to cars. Especially this one. I love it. The radiator is in excellent condition. I don't think that's it. You can tell that the thermostat opens by squeezing the top radiator hose and seeing the flow in the reservoir. The car sat for probably two years. Long story but this was my girls' son's car. The car has never been beat on. I have done plenty of work to it and it has all been straight forward. 2004 131k. I have flushed the system. It seems to me like the coolant isn't flowing. As in water pump. That looks to be straight forward as well.
Thank you for your input. I will twelve volt test that relay tomorrow.