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Heat/AC Blower Issue: Works when car started, but stops if fan speed changed
Ok, this is a new one for me.
First, 2014 C300 4matic Sport, 82k.
I recently replaced the blower motor with the correct one from Autozone (Carquest, not Bosch) due to the blower motor squeaking. No other issues, and I had another MB Blower motor in their prior from a Junkyard car, but it squeaked too.
Fast forward a week, and now the blower will work at the last setting when the car is started and will work at that if the controls are not touched. If you change the fan speed at all, the fan turns off and no mater what you change on the heat/fan control, it never turns back on. You have to shut the car off, then same thing, works at the last level, then stops if you touch something.
Is this a fan control issue, or something else? What should I test? I am not sure if I have the old blower motor. I could not find anyone else with a similar issue here or online.
Thanks in advance.
Last edited by jimmyfloyd; Nov 16, 2023 at 10:39 PM.
Sorta smells like the rectifier...maybe ? Not familiar with facelift C300.is fan rectifier separate, part of motor blower assembly? All connectors firmly reattached, nothing left forgotten, the usual "not working after part replaced" protocol you've probably already checked. The fact it worked for a week points against unless something loosened with fan vibrations. Did I mention I hate electrical problems.
I had a Grand Cherokee where the fan would only work at 1 speed, I replaced the blower motor resistor and it fixed the issue. I think Mercedes refers to it as the regulator.
Heres a parts diagram for my 2010, if you post your vin I can get the ones specific to yours.
Part# 100 I believe.
Looking up 2014 C300 4matic sport I come up with this:
The price is insane. I think I paid $20 for my Jeep resistor.
There must be a way to test the resistor, either using a scanner or even a multimeter.
I recently replaced the blower motor with the correct one from Autozone (Carquest, not Bosch) due to the blower motor squeaking. No other issues, and I had another MB Blower motor in their prior from a Junkyard car, but it squeaked too.
Fast forward a week, and now the blower will work at the last setting when the car is started and will work at that if the controls are not touched. If you change the fan speed at all, the fan turns off and no mater what you change on the heat/fan control, it never turns back on. You have to shut the car off, then same thing, works at the last level, then stops if you touch something.
Is this a fan control issue, or something else? What should I test? I am not sure if I have the old blower motor. I could not find anyone else with a similar issue here or online.
Thanks in advance.
Hey man!!
I got the same issue with a 2011 C180
Changed fan-motor and the regulator.. still the same problem..
Did you solve the problem?
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