Mercedes-Benz Forum banner

1 - 9 of 9 Posts

·
Registered
2013 ML350 4MATIC
Joined
·
18 Posts
Discussion Starter #1
Hello!

I am a new owner of a 2010 C300 4Matic that I bought from an insurance auction - the car was a salvage car due to a front impact.

I have repaired all of the damage, but there is one issue that I cannot figure out.

Immediately upon starting the car, the radiator fan begins to run full speed, even though the car is stone cold. The AC is OFF. The radiator and condenser are BRAND NEW. This problem existed before and after the radiator was replaced.

The fan continues to run at its maxiumum speed, regardless of the engine temperature. I allowed the car to run today from cold to just above 80 deg. C before sutting it off today.

When one feels the upper radiator hose (driver side), it is HOT, and the air blowing near that side of the radiator appears to be hot.

The lower radiator hose (passenger side) is COLD, and the air blowing near that side of the radiator appears cool.

The heat is also turned on full blast, and blows lukewarm/cool air.

What is causing the fan to run full blast, and why is the coolant apparently not circulating?

My only guess is that the thermostat is stuck shut? Does that even make sense?

Please advise if able!
-David
 

·
Registered
Joined
·
254 Posts
I'm not a Benz mechanic so what I'm stating is from an experience I had on my 2008 C300.

Two things will make your radiator fan run on fast. Either a signal that the engine is hot or that the air conditioning condenser (located in front of the radiator) is telling it that it's hot and to run fast to cool it down. In my case, the dryer bag had leaked causing the particles to block up the condenser enough such that it was getting hot and signaling the fan to run faster.

Since your vehicle had been in a front impact collision, you need to be looking around there to see if any wiring has shorted or anything else that would explain the high fan speed. Since it starts when you start the car, I'd think the a/c wouldn't have time to get hot.

As an aside, the tech's put my car on one of their machines to diagnose the problem (before we figured out what was causing it). The machine didn't see the problem. It was only because the mechanic was well trained that he put the gauges on the a/c and found it.

While I was trying to figure this out, on the other forum, someone suggested some kind of controller that's located behind the engine between the engine and the firewall. It was impossible to get to and I eventually gave up.
 

·
Registered
2010 Mercedes S Class Hybrid
Joined
·
3 Posts
Radiator fan blowing high at start up and wont shut off .

Hi did you ever find out what was causing your radiator fan to blow high constantly and heat to blow partially warm?
 

·
Registered
2013 C250 Sport
Joined
·
126 Posts
Hi did you ever find out what was causing your radiator fan to blow high constantly and heat to blow partially warm?
The thread is 3 years old so hopefully he's still around to answer. But this can be from many things. If one fan is bad, a sensor isn't working, etc. It's kind of a fail-safe. There may be DTC codes.
 

·
Registered
2010 Mercedes S Class Hybrid
Joined
·
3 Posts
Yeah, I'm wondering if its the fan control module since there seem to be nothing wrong with the obvious like radiator , temp gauge, thermostat , no check engine light etc. One other symptom I am experiencing is that ever since the engine fan started doing this, the heater wont get hot. SO this makes me think a wire has come loose on the fan control module ,; especially since the fan control module serves the ac/climate control sensor and the coolant temperature sensor. I just wanted to see if anyone ever saw this or what exactly fixed others with similar problems before I take it into a shop and possible be told a lie.
 

·
Outstanding Contributor Always Remembered RIP
216 with everything. 2002 SL500 with everything. 2009 SL500 with everything.
Joined
·
6,543 Posts
This is an air con sensor fault, just like on the 203.
 

·
Registered
2013 ML350 4MATIC
Joined
·
18 Posts
Discussion Starter #7
I'm sorry for not responding for years - wasn't around to read the message.

The fan "reset itself" after driving around for maybe 10 miles. Simply running at idle didn't do it - you had to actually drive miles I guess.

Once I had driven it for a few miles, the fan "settled down" and has run fine ever since.

-David
 

·
Registered
2013 C250 Sport
Joined
·
126 Posts
I'm sorry for not responding for years - wasn't around to read the message.

The fan "reset itself" after driving around for maybe 10 miles. Simply running at idle didn't do it - you had to actually drive miles I guess.

Once I had driven it for a few miles, the fan "settled down" and has run fine ever since.

-David
Three years, that's must be a record, lol. How has the car been otherwise?
 

·
Registered
2013 ML350 4MATIC
Joined
·
18 Posts
Discussion Starter #9
It was a great car for me. Sold it back in April. Repaired the original accident damage and enjoyed the car for about 3.5 years before moving on.
 
1 - 9 of 9 Posts
Top