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Problem With My New 2017 C-Max


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23 replies to this topic

#21 OFFLINE   Plus 3 Golfer

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Posted 24 January 2017 - 02:03 PM

stupid question... why would the outside temperature sensor have any bearing on the operation of the inside climate control?

 

It looks like the problem is fixed, but wouldn't the interior have its own sensor to monitor temperature for the auto setting?

 

As OP indicated there was no faults (DTCs) detected by the climate control software, So, if the set point cabin temperature is above the cabin temp sensor value and the outside ambient temp sensor shows outside is higher than the set point temp, the algorithm will use outside air to bring the cabin temp up to the set point.  Since the outside sensor was giving a faulty high reading, the cabin was not being heated.  Generally, if such software detects that the outside temp sensor reading is bad, the algorithm will use a backup sensor like perhaps the intake air temp reading in place of the ambient temp sensor and throw a DTC.


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#22 OFFLINE   Rick369

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Posted 24 January 2017 - 11:46 PM

stupid question... why would the outside temperature sensor have any bearing on the operation of the inside climate control?
 
It looks like the problem is fixed, but wouldn't the interior have its own sensor to monitor temperature for the auto setting?


I can't answer your question. All I know is when the outside temperature, that displays in the top portion of the Sync 3 screen, exceeded the temperature that the auto climate control was set at, the airconditioning kicked in. In my case the auto climate control was set at 72, the outside temperature ranged from 34F to 38F, yet the outside temperature display registered anywhere from 70F to 120F. When the dealer tech confirmed the condition, it was 8F outside, yet the outside temperature display registered 60F. I've had the C-Max back for 2 weeks since the passenger outside mirror was replaced. Outside temperature display is registering the correct outside temperature and the climate control is working as is should.

#23 OFFLINE   Plus 3 Golfer

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Posted 25 January 2017 - 08:00 AM

AC will come as long as these conditions are met:

 

"The A/C demand message is sent from the SOBDMC over the HEV High Speed Controller Area Network (HS-CAN) to the ACCM . The ACCM engages the A/C electric compressor when all of the following conditions are met:

  • The PCM does not detect excessively high or low refrigerant pressure from the A/C pressure transducer.
  • The PCM does not detect an ambient air temperature below approximately 35.6 °F ( 2 °C).
  • The BCM does not detect an evaporator discharge air temperature below approximately 35.6 °F ( 2 °C)."

So, with auto control on, the modules may allow AC to turn on to control cabin humidity because the ambient temperature is believed to be high.  This doesn't mean the AC compressor is running full out.  It is simply running to keep humidity down.  If you look at the My View screen that shows climate demand, you probably would have seen minimal demand.  

 

This happens all the time for me (AC turns on) even with "real" ambient temps around 55 - 65 F and set point at say 70 F.  So, most times I manually turn AC off.  As soon as you turn AC off, you can feel the rise in humidity in the car and one is more uncomfortable.  Yet the cabin temp. is unchanged.  Auto climate control is simply trying to keep one comfortable by lowering humidity. :)

 

What does surprise me is that evidently the algorithms make no checks as to sensor integrity like emissions systems do and switch to alternative data.  IIRC, for the emissions system, there is a check of intake air temp sensor reading against ambient temp sensor reading.


Edited by Plus 3 Golfer, 25 January 2017 - 02:35 PM.

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#24 OFFLINE   mike884

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Posted 26 January 2017 - 11:07 AM

Oh ok, well apparently the system is smarter than I give it credit for.

 

Something was obviously glitching somewhere, but I assumed it wouldn't even take the outdoor air into consideration. If you ask for heat... it sucks in whatever air is outside and warms/cools it to what you have it set at, based on an inside sensor and ramps the fan up/down as needed.

 

But hey learning something new!


Edited by mike884, 26 January 2017 - 11:08 AM.







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