Weird A/C problem

[plus 3 golfer]

Here's the post showing the installation and the post below gives the part number.  

[bpass]

First post, of course when I have a problem. I have both a 13 and 16 C-max in the family.  Both are SE models. The 16 has developed an AC issue which (at least so far, 4 visits I believe) the dealer has not been able to resolve. The 16 is my daughters car which she traded for after going thru the transmission issues with a 14 Focus. As one can guess she is not very happy.

 

Initial issue was a freeze up (lost air flow), and after finally convincing her to turn of the air for a bit it worked for the rest of the trip. 

 

Now it seems to be an outside air temperature issue. I don't have a good idea where the temp break point is, but believe it is somewhere around 80 degrees. The car never looses air flow now, but will not cool at all above that break point temperature. As I said she has had it in at least 4 times for the issue. The service writers verify that the AC isn't working. Service tech gets the car (and checks out the ac in an air conditioned shop) and can't find anything wrong. I did witness this happen also the one time we were with her when she took it in for service. Lives 200 plus miles away.   90 degree day, ac wasn't cooling at all from the moment we got in the car that had been sitting all night. Pulled it into the air conditioned service bay and while not great cooling it appeared it was working. Doesn't make much sense to me, but puzzles me why the tech can't find the issue.

 

Could this be the Temp sensor. I am sure the dealer doesn't want to change parts unless they can verify the issue. I did point them to the TSB, of course they said it did not apply to the 16's.

 

Any help would be appreciated, it's headed back to the dealer tomorrow, and she would like to have it fixed before the weekend. Has to make the trip home for a wedding she is in, be nice to have AC for the excessive heat wave predicted for our area.

 

I can change the sensor myself once I have access to the car if you think that would be a good first step.

 

Thank you for any help!!!

Edited July 17, 2019 by bpass

[plus 3 golfer]

I'll bet it's the evaporator core temp sensor.   As the ambient air temp increases, the air holds more moisture and the AC unit works harder (runs more) to condense the moisture from the air and to cool the hotter air.  If the sensor is reading too high, the compressor will continue to run, when it should be cycled off to keep the core above freezing, so that it doesn't begin to ice up lose its ability to cool the air even though air is still flowing through the core.  My guess it's not only temp related but also the amount of moisture in the air.  So, lower humidity, it might not ice up completely. 

 

It's an cheap, easy replacement.  I'd just do it, if dealer doesn't.

[bpass]

Thanks for the input, if the dealer can't get it fixed I'll try that this weekend when I have access to the car.

[bpass]

Today the dealer claimed it had 2.6 lbs of Freon instead of the 1.6 the book calls for. I still wonder why it takes 4 or more trips to the dealer to find anything, 

 

I have the Temp sensor ordered and will replace it also once I get access to the vehicle.

Edited July 18, 2019 by bpass

[plus 3 golfer]

Exactly, sounds fishy to me.  Have your daughter look at the service orders as to what was done.  There are DTCs for low and high pressure.  Also, with a scan tool to read pressure PID and pressure manifold gauge, tech can compare actual pressures with sensor pressure.  They can also compare suction pressure with the normal range for a given set of temperature and humidity conditions as long as ambient is above 70 F.

 

Too much refrigerant does not cause the evaporator core to ICE up blocking air flow.  The compressor will cycle off when pressure gets too high and blow warm air.  So, as ambient temp rises, pressure will rise also to the cut off pressure - hence the around 80F.

 

Did she take it in for the blocked air flow?  Someone had to add refrigerant.  They should have evacuated the system and added refrigerant by weight.  And, they should have still checked operations and saw pressure was too high.  The spec calls for 26 ounces (1.625 pounds).  How does someone add 42 ounces of refrigerant and not know it.  

 

Since you will likely never find out exactly what happened, I'd certainly replace the temp sensor as that was the likely the cause of the blocked airflow.  When the extra refrigerant was added, the evaporator would not ICE up since the compressor would shut down at around 80F well before icing would happen.

[bpass]

Bought the car low mileage used so not sure on any fills or recharge. The daughter is not very good about keeping the paperwork so that  will be no help. Might be able to get copies from the dealer, but not sure it is worth the hassle.

 

She left it at the dealer last night and told them to verify that it is working correctly today before she picks it up. Hopefully they will follow thru. I will change the sensor once I get access to the car.

 

Thank you for the guidance!!!

[C-MaxA2]

That's why a lot of us refer to dealers as 'stealerships'.  Can't tell you how many times they clearly decided to pursue the most profitable path for them irrespective of what is really wrong and what is really needed.  'Throw parts at the problem until we hit the right one'.  

[Lazette]

I have a 2014 ford cmax energi i changed the compressor and the a/c still dosent blow cold air. Why?

[RRF2]

The temp sensor replacement makes the most sense to me. Usually the simplest solution is the most plausible. My air flow gets blocked sometimes, when I’m driving with the AC on for a while. I turn the AC off, and keep the fan running. Once the air flow starts to pick up again, the air will come out cold, which means that the blockage is ice, and it’s cooling off the air as it melts. Once it’s melted, the air starts to warm up, and the air flow is back to normal. So, it seems logical that ice is blocking the coil when the issue occurs, and that a new sensor could help. Otherwise, just run the fan without AC until the air flow is back to normal, then turn the AC back on.