kaybal

Hello Guys,

I started noticing that my car was showing the temp symbol for few weeks but the temp gauge wasn't shooting up but after few weeks it started shooting up and car is overheating.

I took it to Mercedes for diagnostics and they told me my fan needs to be changed. I then start noticing that the fan will not roll sometimes or started rolling after I shut that the engine.

I bought new fan and install it. But still the car was overheating. So I open the hood to see what the new fan was doing. I notice the fan wasn't blowing as fast as it should. It was just rolling slowly. When I start the car in the morning, the fan will not blow and when the engine start heating up the fan will start blowing gently. One day the car was extremely hot that it was fuming, I thought it was the radiator water that was over heating and smoking out but then I realized I heard a little pop sound and that smoke came and it was smelling which I realized later that it was the Freon because after then the A/C wasn't cool anymore. The compressor is working but not cooling. I try to add Freon to the car put when we plug it in the reading on the Freon can says there is Freon in the car but still its not cooling.

Now the question is why is the fan not blowing fast/high? If I remove the fan plug and put it bag it blows a bit faster then continue slowly.

What else can be wrong with the car?

Plutoe

Post you VIN if you want correct information on the car!

kaybal

WDDDJ72X79A147740

Plutoe

All the following assumes that the OP purchased new parts and not a junk yard fan--bla bla

On your 273 the coolant management is accomplished by the ECU which receives signals from various sensors including the coolant temp sensor and manages the thermostat for 80-100C and after 110C is wide open.

After 100C the aux electric coolant fan with intergrated control unit is actuated. The fan is also actuated if a high refrig temp is sensed.

Therefore you have two sensors you can test---the three disk thermostat(test ohms=15.2 + or -1.5) or coolant temp sensor.

If it were me I would test both sensors and flush the radiator(you need a special tool to test the fan so forgetaboutit) change any faulty sensors and buy the wife a hotdog!!

kaybal

Thank you very much. Someone said I should check the sensor as well. Now I have bought the sensor but it seems all the diagram I'm seeing online doesn't help. My sensor is not located where all the diagrams are pointing. I think they are for the older models before 2008. Mine is a 2009.

Please can you help with the location?

THanks.

kaybal

My mech told me that if the coolant temp sensor is bad, the dashboard indicator will not work as well. I can see on the dash that the car is overheating because the dash gauge is rising .

One new thing I found out yesterday was that, when the fan is working the car is not overheating. I left the car idle for long time and the fan started spinning fast and the car was not overheating. I even recharge the Freon and the AC is working fine. But then here comes the problem. I switched of the engine and start it back up and the fan rolled a bit and stopped. I was waiting for the fan to come back on because I know the car is hot but it wont. So I unplugged the fan and plug it back in and it started working and rolling fast to cool the engine. I tried the same thing again switch of the car and restart but the fan will not work until and unplugged it and plug it back in then it started working and cooling the engine.

This is a new fan well (aftermarket) I bought after Mercedes service center diagnosed that the old fan was bad. So is this a bad fan or the control module?

equitiesguy

You can test the fan through STAR by activating it at 100% and letting it run. If it doesn't, you have your answer. The fan module is attached to the fan itself, and activated by the ME signal.

kaybal

Thanks for the reply. I have STAR I tried to do that but I can't seems to get the Menu to get to where I can test the fan..
Do you know under what menus I can do this please?

equitiesguy

Motor Electronics ---> actuations. It's in the list.

kaybal

I tested the fan. Sometimes it rolls sometimes it doesn't. I send it back and got a replacement. Now the replacement has the same problem. When I tested it with STAR, it gives this clicking sounds like its trying to roll and this happens like 7 times and then it rolls and works up to 100%. I stopped it and tested it again, it does the same thing make a clicking sound, roll a lit bit, make a clicking sound roll a little bit after doing that few times, it didn't roll. Then I tried it again, then it does the same, make clicking sounds while trying to roll then it starts rolling. So basically, I tried the test 7 times, the fan worked only 4 times. The other 3 times, it starts to roll with a clicking sound and stops and do that over again for about 7 times each time then won't roll.


I don't know if the fan is now the problem because this is a replacement fan now behaving like the previous one.

kaybal

I tested the fan. Sometimes it rolls sometimes it doesn't. I send it back and got a replacement. Now the replacement has the same problem. When I tested it with STAR, it gives this clicking sounds like its trying to roll and this happens like 7 times and then it rolls and works up to 100%. I stopped it and tested it again, it does the same thing make a clicking sound, roll a lit bit, make a clicking sound roll a little bit after doing that few times, it didn't roll. Then I tried it again, then it does the same, make clicking sounds while trying to roll then it starts rolling. So basically, I tried the test 7 times, the fan worked only 4 times. The other 3 times, it starts to roll with a clicking sound and stops and do that over again for about 7 times each time then won't roll.


I don't know if the fan is now the problem because this is a replacement fan now behaving like the previous one.

kaybal

Does anyone have a clue to what this mean please?