A/C works sometimes
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Joined: Nov 2021
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From: DFW USA
2012 C250 Turbo M271 EVO, 08 X3, 08 328i
A/C works sometimes
I have replaced the blower motor resistor on my 2012 c250 a few months ago for the reason of intermittent working A/C and now the issue has returned again. When I turn the A/C on, it sometime works and sometimes does not. When it does not, I hit the area under the glove compartment with my hand in order for the a/c to work. It is the same issue again. The A/C worked fine for months before the same issue returns. I checked for lose connection but all were OK. Is it possible the resistor got bad again? I paid a bout 50 dollars for after market part from eBay
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From: Walnut Creek, CA
325Ci, 325Cic, C300
I have replaced the blower motor resistor on my 2012 c250 a few months ago for the reason of intermittent working A/C and now the issue has returned again. When I turn the A/C on, it sometime works and sometimes does not. When it does not, I hit the area under the glove compartment with my hand in order for the a/c to work. It is the same issue again. The A/C worked fine for months before the same issue returns. I checked for lose connection but all were OK. Is it possible the resistor got bad again? I paid a bout 50 dollars for after market part from eBay
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2021 GLB250 FWD, 2023 GLA250 FWD, 2013 C250, 2015 GLK350, 2005 ML350SE, 2003 E320
I have replaced the blower motor resistor on my 2012 c250 a few months ago for the reason of intermittent working A/C and now the issue has returned again. When I turn the A/C on, it sometime works and sometimes does not. When it does not, I hit the area under the glove compartment with my hand in order for the a/c to work. It is the same issue again. The A/C worked fine for months before the same issue returns. I checked for lose connection but all were OK. Is it possible the resistor got bad again? I paid a bout 50 dollars for after market part from eBay
Do you have access to a high end scanner to see if any A/C codes show up?
A long shot would be a very worn blower motor with bad brushes or an intermittent internal fault.
Thread Starter
Member
Joined: Nov 2021
Posts: 138
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From: DFW USA
2012 C250 Turbo M271 EVO, 08 X3, 08 328i
The control voltage to the blower shows 5 to 6 volts and the refrigerant pressure between 10 and 14 bars
what is the normal?
i could get codes on Icarsoft
Last edited by Marktee; Aug 31, 2022 at 11:57 PM.
Thread Starter
Member
Joined: Nov 2021
Posts: 138
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From: DFW USA
2012 C250 Turbo M271 EVO, 08 X3, 08 328i
Would it be possible the blower motor is the culprit? Is it possible the brushes are bad? I pound using an open hand on the area under the blower to try to make it work. Sometimes it does work. Before I spend money on removing the Freon and charge it again. Would a bad blower cause symptoms like intermittent working blower? I got between 10 and 14 bars of the refrigerant pressure in the system, would that be sufficient? It is very cold When it is working though.
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2021 GLB250 FWD, 2023 GLA250 FWD, 2013 C250, 2015 GLK350, 2005 ML350SE, 2003 E320
Your refrigerant pressure is fine. I don’t know what the control voltage should read. It would be interesting to see if you’re getting any A/C system codes. A bad blower motor could certainly cause an intermittent air flow. So would a bad blower resistor. The pounding could be jarring an intermittent open circuit back into place. But that circuit wouldn’t necessarily be in the motor, but would be connected to it. I’m just guessing here, but wondering if the problem could be in the controls under the radio. Over decades of MBs I’ve never had a bad motor or a bad resistor, but have had one bad HVAC control unit.
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The problem is the blower motor. Rule of thumb, always replace both the motor and the regulator. Since you already replaced the regulator, just replace the blower motor.
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Thread Starter
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From: DFW USA
2012 C250 Turbo M271 EVO, 08 X3, 08 328i
I removed the blower motor and cleaned it thoroughly from the extensive gunk it had. It has been already a week since the cleaning and the blower works every time. What a relive....
Now the next thing I want to ask your opinion is that when the temperature is hot outside, the A/C blows straight hot air for a while and may be 2 miles before I guess the compressor kicks in and starts blowing cold air.
Now the next thing I want to ask your opinion is that when the temperature is hot outside, the A/C blows straight hot air for a while and may be 2 miles before I guess the compressor kicks in and starts blowing cold air.
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2021 GLB250 FWD, 2023 GLA250 FWD, 2013 C250, 2015 GLK350, 2005 ML350SE, 2003 E320
The other cause would be gas on both sides of the system which would be a refrigerant charge issue. But your pressures are right so your charge should be okay.
If you are sure it’s not very high temp in the passenger cabin, e.g. the car is parked in a garage, then the car will need to be started then the hood opened to see if the compressor clutch is engaged. I think your iCarSoft can be used to see where the bad component is.
