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I have changed the battery 2 months ago and last friday the a/c stopped working and the cooling fan where running at full speed.
I have been to a workshop for a diagnosis and they have told me there were an error with a high electricity jump, maybe from the time I have changed the battery, even if I have used another electricity connection but the plus should be disconnected last from old battery and connected first to the new one.
So, he deleted the error, reconfigured the software and the car works as it should be without replacing anything.
Replacing with a used part does not seems to be a good solution because, if the old one was defective, the used one may damage soon as well or when the battery is changed again (3-4 years from what i have noticed).
Try to get to a workshop which can do a proper diagnosis, using the original MB software.
I am happy I did not paid 1000 dollars to replace the climatic console.
My car just went in to the dealer for same symptoms. Radiator fan on high at start up, climate control buttons no lights. Battery had previously run down to zero. I did end up getting a used market switch bank and replaced the HVAC module to no avail. Although with the new parts, the radiator fan stopped turning on and I gained some functionality climate control buttons but it’s still noT working 100% correct. Maybe just need some coding as I read above about the HW/SW may need updating? Will see.
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 here....
2012 mercedes c350 w204
Last edited by collectivejoel; Sep 25, 2023 at 07:01 PM.
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
I know this is a thread revival, but my daughter had this happen to her 2013 c350 this morning. Of course it was very cold out, 20 degrees F, and the climate control panel was blacked out. Within 3-5 seconds of starting the car, you guessed, it the radiator fan went to full speed.
I'm going to check the #12 fuse when I get home, hopefully it's just that. If not, I'll check the driver sill panel as shown by collectivejoel.
So I got home, and checked to see if it was still not working, and confirmed it.
I pull the 7.5amp #12 fuse, and it checks fine, but still replace it. Start the car, and all is well.
I used a voltmeter, and the fuse was fine. Maybe pulling the fuse and putting it back in 'reset' the module. We will see.
Just to be safe, I showed my daughter how to do it, and put a pair of pliers in her car.
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