knightrider1

Hello Everybody!
I have a w204 C200 and I have noticed that the radiator fan has stopped coming on when the engine heats up. For example, my diagnosis machine shows the refrigerant temp is 109 C and the radiator fan not start.
However, the same situation, I turn the AC on and the radiator fan runs correctly and the refrigerant temp decrease to 90 C in about 20 seconds.
The diagnosis machine don't show me any code error. The thermostat is ok.

I have search in the forum and I have found several post with similar problem, but with no solution or i don't understand.

Could you please help me to find the problem?


Thanks a lot!!

JettaRed

iTrader: (1)

Seems like the car is within the allowable operating temperature. Check your Operator's Manual.

knightrider1

Thanks for your answer.
I understand , as you say and the manual, that the car is within the allowable operating temperature.

But I think that from range 90 to 108 there would be a temperature that the fan should start to make the temperature decrease to 90.
Or the temperature has to rise to 120 to make the fan to start? I don’t know. Because of this i think there is a problem with the radiator fan.

Thanks again

JettaRed

iTrader: (1)

Well, what would the problem be?

Maybe if the A/C is on, the fan comes on anyway and regardless of the coolant temp. Maybe it bypasses the temperature trigger. But, if your scanner is reading coolant temp, then it's not the temperature sensor. And, if the fan does come on with the A/C, it can't be the fan. Maybe there is a separate thermostatic switch that turns on the fan because of temperature. I'm sure someone will chime in with the answer.

TimC300

What is the coolant temp?

Are you saying the fan will not come on and the car will overheat?

Have you opened the coolant reservoir and checked the level and condition of the coolant?

Have you worked on the car lately, anything?

knightrider1

Hello!

I have done a test, so it may help to recognize the problem.
- I start the car and the AC is OFF.
- With the car parked, mantain the revolution to 1800 rev, so the refrigerant temperature start to increase.
- After a few minutes, the temperature raises to 107 C. At this moment, the radiator fan starts.
- Then the temperatura decrease to 106 C and the radiator fan stop.
- After a while, the temperature raises to 107 C and the radiator fan starts again, until the temperature goes to 106 that it stops.

This action is repeating all time (When the temperatures goes to 107 C the radiator fan start, and when the temperatures goes to 106 it stop.)

Note that from the car starts until the refrigerant temperature goes to 107 C, the radiator fan not start. (it only would starts if i would put the AC on)

I think that the radiator fan should start before 107 C or if it starts when it is 107 , not to stop until the temperature is 90 (Now stops in 106).


The answers to your questions:
- The coolant level and the condition is OK.
- I havent workd on the car.

Thanks for your help.

TimC300

I'm wondering what you mean when you say "refrigerant" temp. Are you talking about the coolant, or the AC refrigerant?

Where are you getting the temp numbers from, an OBD scanner or from the dash temp gauge?

What is your dash temp gauge showing? Mine is always around 90 c when driving.

Which obd scanner are you using, is it specifically for Mercedes?

There is nothing really wrong with the car, except you don't think the fan is turning on when it should? No codes, no check engine light, the car is not over heating? Is the AC working properly, blowing cold air when you turn it on?

knightrider1

Hello, sorry about my english. When I say refrigerant temp I mean coolant temp.
The temp numbers I get from an obd scanner (KTS BOSCH)
The dash temp gauge is showing always 90.
I have no code and no check engine light and also the AC work properly but I have notice some items that make me think there is a problem.
The items are:
- The engine is so hot. I bought the car three years ago, and I have never notice the engine is so hot.
- When the engine is so hot the engine smells like a coolant liquid but i can't see any coolant leak.
- When the engine is so hot the radiator pipes (IN and OUT) are very hard if you touch them. That seems the engine is working with an excesive presion.

These items, when the radiator fan is on don't occur.
So, If i don't put the AC on, the car is always running with a coolant temp higher than 106.
I would know what sensor or component is envolved in the radiator fan start and stop, so i could check it and renew it if necessary. Or also know the temperatures range when the radiator fan is ON or OFF from a workshop manual or similar. Or any collegue that could do the test i have done to see i if he have the same results.

Thaks for all

doniv

I am also facing the same issue nowadays but one thing I noticed is now it is cold climate here unlike few months back. I remember my radiator fan was running multiple times even after I switch off the car but nowadays it is not happening at all and I did some recent repairs to the car, I went to them and told my concern and they checked and told there is not issues. One thing I noticed is the ODB scanner showing coolant temperature sometimes reaches >101 and if I switch ON the AC it comes down to 80 to 90 C.
I doubt there is something to do with the outdoor temperature also, that is the only guess I am having now.

randall977

When the a/c is turned on it activates the radiator fan (at 40% I think). The fan should also be activated independently of the a/c as the engine warms up. The needle on the instrument cluster should never go above half way (80 degrees?).

I’m having this issue (like many) and am struggling to find the cause. My code reader is able to call on the fan, but the engine won’t.

CaliBenzDriver

Ok, so your fan activation test is successful,
the temp display gauge appears normal,
but the ECU does not seem to be able to run the fan.

Can you read the Coolant temperature data under ECU ??

randall977

Thanks for the replies.

I couldn’t find the temperature with my new code reader. My cheap OBD2 scanner showed the temperature to be as the instrument cluster…but then it would as it’s taking the reading from the same source as the instrument cluster.

I read someone’s post on the SLK forum where their instrument cluster was correct, but the sensor wasn’t triggering the fan. They replaced it and everything worked again.

I have ordered a new one as they’re cheap, but changing it on a kompressor engine looks difficult. I could renew the thermostat too as it would probably be easier.

CaliBenzDriver

You know, replacing random parts is not how you're going to fix this.
First find out what your engine coolant temp measures.

Anyway these hot parts don't last for ever. Early OEM replacement can only be helpful

randall977

Thanks for the advice - very sensible.

It’s not totally random though, as I have established the problem to be either the temperature sensor or the ECU (or wiring to the ECU). The ECU would be worst case scenario, but I need to know if my scanner tells the ECU to operate the fan or if the scanner produces its own signal to operate the fan to find this out.

CaliBenzDriver

The scanner clearly order the module under its control to comsnd it's own outputs. Only computers have local connections where they are.

The scanner uses CAN-D gateway to remotely connect to every other module.


​​​​​​Fan test:
You use a scanner to activate the radiator fan at variable speed. If that test works right it neans your coolant temperature criteria is not met.... bad sensor probe, bad sensor harness...

CaliBenzDriver

here a chassis network of MB found in WIS and Xentry

Set of separate networks of modules

Your big fan is still connected to ECU digitally to receive PWM control signal.
Newer MB car fans are independently messaged like our windshield wiper module over LIN data.

randall977

I thought that might be the case - so the ECU could be at fault. There are no fault codes btw.

I'm thinking that the tempertaure sensor (which is a few mm from the kompressor pulley) is more likley to be faulty - though as mentioned it seems to be outputting the right temperature to the instrument cluster. On the other forum, this was the case, but replacing the sensor cured the problem. It looks like a horrible job - I can't find a write up on it. If access were better I could swap it over in one minute.

CaliBenzDriver

reason why you don't want to guess without testing is MB can be fixed without parts... when poor connections are involved:

1. Oil-in-harness
2. Oxidized pressed-pins
3. Painted GND

In general you'll find that if you don't test before swapping parts, you will afterwards ...
sometimes it's right also to go into "tune-up mode" and change all the cheap parts...

CaliBenzDriver

The gauge is liar gauge! It's not connected to the ECT but to ECU data through ICluster bus.

Read the Coolant sensor in the ECU module. This will be pivotal pass/fail results.

randall977

I really appreciate the advice as it’s really frustrating not being able to drive the car 😢.

I couldn’t find the temperature reading on my new scanner, it seemed to suggest -176V (or similar) as the temperature - I assumed that I was not understanding what I was looking at!

I do have a test plan… Get the new sensor, connect the sensor wires to it (extend them), put it in very hot water and see if the fan comes on. Does that sound sensible?

randall977

I had gas put in the a/c (it had been emptied by a garage when they changed the radiator) so the fan does now work with the a/c on. So at least I can now drive the car without it getting too hot under the hood…or in the cabin 😅

CaliBenzDriver

.... that sounds like a good plan.
In the end you will know if your engine coolant sensor output reacts in function of temperature.

​​​​​​MB uses remotely heated thermostats. This heater is the plug sticking out of Tstat.