I hope someone can help me with my 98 C280. I have owned it since it was new and I take methodical care of it. However, About a month ago, it started running hotter than it has at any time in the last 3 years. There is no apparent damage to the radiator or cooling lines and all frontal shrouds are in place. The temp has never been above an indicated temp of 80-85C. Now, the Temp is always 85-95C. The electric fans now run in high speed a lot more often than they use to and the front right quarter panel is extremely hot to the touch. I verified with a calibrated temp meter that the temp of the top cooling line at the engine is running between 88-93C at idle with an ambient temp of 75F and AC on. The dealer has replaced the coolant tank cap, flushed the system and changed the thermostat. Oil level is in spec. (Mobile 1 10-30). The dealer states that that temp is in spec for my car and are happy with the way it is running. However, they have no explanation why the outside front right quarter panel is so hot or why the temp is indicating higher and why the cooling fans are running more often. The car has never had any damage or mods done to it. Any suggestions would be appreciated. Should I insist they change the water pump? The car is still under warranty. Thanks!

Brian

Hi
This is a common problem as many professinals talked here. You may have a burned fuse in the low speed fan relay.
Here is my experience on C220.
Find the relay box under the hood in driver side right next to fuse box. Screw off 5 screws then open the cover. You can see a relay with 15A fuse, this is the one for low speed fan. Replace it with 25A or 30A cause 15A is too conservative for the current the fan consumes.

I also know it from this great site. Thanks to all who contribute to this site.
I am so glad to have my first post here.

Charles
1994 C220
TAIWAN

I know this is an old thread, but I seem to have the same problem. My '98 C280 runs about 90c to 94c and the coolant fan is either full on or full off.

I tried to use your description to find the lowspeed relay/fuse, but mine has several fuses and relays in the described box!

Can someone with a layout tell me which relay and fuse is which?

Thanks again guys!

Kid

In '98, the fans are no longer limited to low speed/high speed. Electric fan speed is infinately variable and based on coolant temp and refrigerant pressure and is controlled by the Motronic control unit.

On the '97 model year, the lowest trip point based on coolant temp was 95C. 90-94C is normal, I would be concerned if the temp did not get to the 90-95C in traffic, because then something would be wrong.

__________________
Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

Thank you so much for the information!!!! I feel better now!

Kid

Charles was right on the money with my problem - Thanks!

Hi everyone! Just an update - I have a 1995 C280 with only 63k miles and have been having the same coolant temp problems since I purchased the car a year ago. I went through all of the normal updates: new thermostat, flush and drain, even purchased from JimF the "cool harness" - but the real symptom never changed.

There was another post (Charles ) where someone mentioned that in the low speed fan circuit for his 1994 C220 - there was a relay that controled this circuit in the section "behind" the fuse box on the drivers side of the engine compartment. This relay has a "piggy-back" fuse installed at the factory as a 15A fuse. The indication was that the fans draw over 20A at times and that a 25A or 30A fuse should be placed here.

When I looked - that was my problem - a simple fuse replacement would have solved the problem.

Here are the symptoms:
1) At some temp the low speed fan circuit should turn on the fans and they should run continuously until the temp gets low enough to turn them off - or - the high speed circuit kicks in.
2) If your fans only turn on and of in high speed and typically stay on only for 20 seconds or so until extreme high temps are reached (110-120 degrees C) and you never see a slow speed fan condition. CHECK THIS FUSE
3) Most of the time the temp stays between 85-95 degrees C when operating at speeds of 30 MPH or more, but then in stop and go traffic - or low speed driving - temps can move up to over 100 degrees C and stay there until "something changes" (no clear indication of what made the temp go down). CHECK THIS FUSE

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My cooling fan runs only at the slow speed is there a fuse or relay that is bad??

slow speed only? that's new.
u should really check the fuse on 'em.
coz the low speed fan is usually triggered only by the refrigerant pressure and not the water temp.

__________________
w202 c200 malachite green
w115 200 green

Engine cooling fan is computer controlled. Most likely a problem with that control unit.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
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Retired Moderator

Is there a problem with your temp? If the temp is fine then that could be why the fan only runs on the low speed.

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

I have owned this car since new, it runs at 90c when you stop for a traffic light the temp starts to climb and when you start moving the temp comes down. The high speed fan never comes on like it used to.

if your car heats up at a stoplight and then cools down when you take off again,[assuming that the cooling circuit is full] the radiator tubes might be shrunk.

__________________
David S Poole
European Performance
Dallas, TX
4696880422

"Fortune favors the prepared mind"
1987 Mercedes Benz 420SEL
1988 Mercedes Benz 300TE (With new evaporator)
2000 Mercedes Benz C280
http://www.w108.org/gallery/albums/A...1159.thumb.jpg

Hi, I have a 94 C220 and sometimes in the morning when I first start it the cooling fan comes on. Ill drive it for a little and it may turn off. The temp is fine, no strange changes. Could this be a fuse?