2004 CLK500 Coolant Fan will not RUN
Thread Starter
Newbie
Joined: Feb 2020
Posts: 7
Likes: 1
2005 CLK500
2004 CLK500 Coolant Fan will not RUN
So the car has not seen the road in a while. The problems initially started with the radiator exploding after the battery died due to an alternator failure. Eventually I ended up replaceing the Alternator, water pump, hoses, thermostat, cooling sensor and battery . Had it in my garage to check the AC but had to leave a few days for work.
While I was away my brother pulled it out and left it in the driveway. He didn't realize I had the fuse cover off . So yea it rained and the ECM was toast. ( wouldn't crank and Coolant fan just spun in turbo mode). So I got a salvaged ECM and had the chip moved over and the car started right up and seemed to run fine. However I am getting one message saying check low coolant levels and the coolant fan will not turn on at all (even with the AC on) .
The coolant level is full in the reservoir , and other than the fan not running everything seems ok. I can run the car for 15-20 minutes until it gets just past 80C but I am reluctant to let it get hotter.
If I Pull RELAY R, the car will not start but the Coolant fan will spin at high speed so I know the fan has juice and that it will run I just don't know what could cause it to not work .
Any ideas out there ? Not sure if there is a FAN relay which could have gotten water damaged as well.
As a last resort I may just directly power the fan to my ignition so it runs all the time at high speed, its not ideal but it will get be on the road if I can't figure it out.
While I was away my brother pulled it out and left it in the driveway. He didn't realize I had the fuse cover off . So yea it rained and the ECM was toast. ( wouldn't crank and Coolant fan just spun in turbo mode). So I got a salvaged ECM and had the chip moved over and the car started right up and seemed to run fine. However I am getting one message saying check low coolant levels and the coolant fan will not turn on at all (even with the AC on) .
The coolant level is full in the reservoir , and other than the fan not running everything seems ok. I can run the car for 15-20 minutes until it gets just past 80C but I am reluctant to let it get hotter.
If I Pull RELAY R, the car will not start but the Coolant fan will spin at high speed so I know the fan has juice and that it will run I just don't know what could cause it to not work .
Any ideas out there ? Not sure if there is a FAN relay which could have gotten water damaged as well.
As a last resort I may just directly power the fan to my ignition so it runs all the time at high speed, its not ideal but it will get be on the road if I can't figure it out.
Thread Starter
Newbie
Joined: Feb 2020
Posts: 7
Likes: 1
2005 CLK500
Super Member
Joined: Jan 2015
Posts: 920
Likes: 46
From: Worcestershire UK
W124 260E
There is a small relay in your fuse box under the hood that is for the fan .. First check fuse 38 and 41 in fusebox under the hood drivers side or depending on what side youe steering wheel is on .
Last edited by optimusprime m1; Feb 18, 2020 at 10:38 AM.
Trending Topics
Thread Starter
Newbie
Joined: Feb 2020
Posts: 7
Likes: 1
2005 CLK500
I actually have an extra fuesbox with relays that I got with the ECM so I had swapped out the relays .
Everything seems in order... So Its looking like either I have a problem with the control wires going to the fan or the ECM is the problem. I'll get it on the lift and try to apply some voltage to the control wire and see if the fan starts spinning.. Worst case I'll just have to put one of the external fan controllers on it and bypass the ecm.
MB World Stories
The Best of Mercedes & AMG
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun
Verdad Gallardo
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Verdad Gallardo
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
Thread Starter
Newbie
Joined: Feb 2020
Posts: 7
Likes: 1
2005 CLK500
I connected my Autel. Did not see any codes. I was able to perform live tests with the coolant FAN where I could turn it on and change the speed .
So I knew the computer could talk to the fan and the fan ran fine, it just would not run outside of diagnostics.
The Temperature sensor reported the proper temp so I never thought to check it. It was replaced at the same time the alternator since the temp was not reporting with the old one. The new one reported temp but we but i never had the opportunity run it for more then a few minutes before the ECU died in the rain.. Turns out as soon as I disconnected the temp sensor the fan started working so it looks like it is the problem. I'll get another one and check it out but at least I can drive it now ( even though the fan runs like a jet)
So I knew the computer could talk to the fan and the fan ran fine, it just would not run outside of diagnostics.
The Temperature sensor reported the proper temp so I never thought to check it. It was replaced at the same time the alternator since the temp was not reporting with the old one. The new one reported temp but we but i never had the opportunity run it for more then a few minutes before the ECU died in the rain.. Turns out as soon as I disconnected the temp sensor the fan started working so it looks like it is the problem. I'll get another one and check it out but at least I can drive it now ( even though the fan runs like a jet)
