Cooling fan starts running when started from cold and climate control system is dead
 

Hi Guys

I need your help!

My MB is 1996 E230 estate W210 series of 140k mileage with auto transmission and air conditioner. Recently the climate control system appears to be dead. No air - cool or hot - comes and all switches on the instrument cluster do not work at all. My first response to that is something about the fuses. But all the fuses are OK!

However, I have also noticed the followings:
(1) The cooling fan starts soon after the engine is started from cold, and the cooling fan then never stops until I switch the ignition off! That is very abnormal since the cooling fan should only run when the engine temperature is very hot - not when the engine is cold.
(2) The temperature gauge shows no overheating. The engine keeps at 80 degree centigrade - the normal operational temperature for engine (I have done a road test for 10 miles in 15 minutes).

What I think the possible causes of the problem could be:
(A) A faulty sensor (but do not know which one) sends a wrong message to the electronic control unit that shuts down the climate control system, including the air conditioner, and instructs the cooling fan to be on all the time!
(B) The electric cooling fan control unit (located under left-hand front wheel arch according to Hayes manual) is faulty.

Below are the conditions of my car relevant to the situation:
(a) The coolant level and condition are normal (renewed 3 months ago).
(b) Not a single warning sign flashes on the dash board.
(c) The air conditioning sensor located in the thermostat housing area appears OK.
(d) The condition of the auxiliary belt is good.

I have stopped using the car to avoid engine overheating. I wonder if somebody can point me out the problem and advise me what to do if I intend to repair it in a DIY manner. For any further information you may need, please shout.

Looking forward to seeing your shared experience and advise.

Regards
Sean

RE: Cooling fan starts running when started from cold and climate control system is dead
 

Well a few days ago I started experiencing some of the problems you have on my 86' 420 SEL (or W126). The cooling fan turns on a few seconds after I start the engine when it's cold and stays on. It shouldn't do that seeing that it's not even close to overheating. I've also noticed that my air conditioning doesn't work, it only blows hot air instead. I took it to my mechanic (where it's at right now being fixed) and he said it could be the sensor which needs to be replaced and the air condition needs to be recharged. Not a single dashboard light comes on either. But I think the fan has something to do with everything somehow... But I dunno I'm 17 and I'm not an expert on these cars, that's my two cents.

RE: Cooling fan starts running when started from cold and climate control system is dead
 

Hi MBenzS600

Thanks for your experience. I should now trace some kind of sensor that causes my problem.

In the meantime, hope some guys can share their experiences and/or give advises.

Regards
Sean

RE: Cooling fan starts running when started from cold and climate control system is dead
 

Most like you will find the problem is caused by the water temp sensor. I have an older Saleen Mustang and the Mercedes is much better, especially on your back! The Saleen I used for drifting now a days.

RE: Cooling fan starts running when started from cold and climate control system is dead
 

I did a search and came across this tread. I'm experiencing the same problem. What is the fix? Is it a sensor? BTW, my car is a 1991 420 SEL.... 30K miles

RE: Cooling fan starts running when started from cold and climate control system is dead
 

Hi Guys

The problems of my MB are fixed!

I hope it is not too late to share the experience so that in case of the same problem you can fix it yourself quickly saving plenty of money in repair.

After lots of research over technical websites, technical forums and Haynes manual, I considered the fan and its related sensors should be functioning OK. It should be some kind of connection that caused the whole issues. As the only thing that I had not done was the Heater Control Panel (above the radio), I decided to shed some light on it. By removing and then refitting it, the air conditioner and the fan work magically back again. My conclusion is that the problems lie on the 2 LOOSE opearting rods at the back of the Heater Control Panel. Fitting the 2 rods properly solves the problems.

Hope this leaves you a good reference.

Regards
Sean

bump.... I have replaced the climate control unit for 5 different ones, from glk 350 to c350. they all work and still ....sometimes there is no power to the control unit intermitly ( Radiator fans come on immediately when the control unit loses power)


this can happen when driving also with rear defrost on. starting to think its the AC pressure line faulty to tell the radiator fans to turn on constant... which then tells the control unit to show off/cut power

has anyone figured this out. climate control unit and fuses are not the issue....

vehicle is 2012 c350 w204

HI everyone.... I have solved the climate control fan not working/ radiator fan at high speed :)

Under the the driver side (carpet where the rubber and kick panel are) there is a little circuit board. this gets wet from the moisture damper in the carpet and water runs down the tab, through the hole into the curcuit board, and connections.



THIS WILL DISABLE CLIMATE CONTROL UNIT POWER and turn the radiator fans on when that happens

I have attached pictures attached the location and the board, i dried the unit out with vacuum and heat gun carefully not to melt. reconnect it and its works. perfect


w204 c350/300 GLK 250/350https://cimg1.ibsrv.net/gimg/mercede...de4f452950.jpg
https://cimg2.ibsrv.net/gimg/mercede...335fa9f641.jpg

Radiator fan runs when engine is cold
 

Radiator fan runs when engine is cold. Reasons and Fix. Read Here

Inspect the fuse and relay related to the climate control system in the vehicle's fuse box. A blown fuse or faulty relay could cause the climate control system to fail