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AC Issue

4K views 17 replies 7 participants last post by  mx2forty 
#1 ·
All, seeking advice with an ongoing AC issue.
2017 Mustang EcoBoost with automatic climate control.
I took it to Ford a few years ago with an intermittent cooling issue. They diagnosed it as a temperature sensor on the passenger side. Fixed it and the tech said he ran it while measuring the temperature out of all vents and it measured correctly. Fast forward a few years and the issue never really changed. It has still never worked right. I know that there are issues with compressors on the Mustangs but I am not sure that is the issue.
The air will blow cool and then it is like a blend door closes and the airflow or mixture is being blocked. This does not seem to happen on short trips but more often happens when you have been on the road for 30 minutes or so. If you turn off the whole system while driving and roll down the windows for 5 minutes, sometimes it starts working correctly again when turned back on. I am at a loss because it can work well but never stays working well.
Does this sound like a compressor? Has anyone else had anything like this? We love the car but this is maddening.
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#2 ·
All, seeking advice with an ongoing AC issue.
2017 Mustang EcoBoost with automatic climate control.
I took it to Ford a few years ago with an intermittent cooling issue. They diagnosed it as a temperature sensor on the passenger side. Fixed it and the tech said he ran it while measuring the temperature out of all vents and it measured correctly. Fast forward a few years and the issue never really changed. It has still never worked right. I know that there are issues with compressors on the Mustangs but I am not sure that is the issue.
The air will blow cool and then it is like a blend door closes and the airflow or mixture is being blocked. This does not seem to happen on short trips but more often happens when you have been on the road for 30 minutes or so. If you turn off the whole system while driving and roll down the windows for 5 minutes, sometimes it starts working correctly again when turned back on. I am at a loss because it can work well but never stays working well.
Does this sound like a compressor? Has anyone else had anything like this? We love the car but this is maddening.
View attachment 42570
Possible air blockage due to evaporator coil being iced over. Most common cause, low refrigerate level and/or dirty/restricted evaporator coil.
 
#5 ·
If your a/c compressor is short cycling then it will be also low on refrigerant. That also causes icing as the evaporator temp should stay internally at about 38 to 42. When it starts again stop lift the hood and see if compressor is running or just turning on and off or short cycling as I call it.
 
#8 ·
Ok, I feel like this will end with me pulling the dash out and replacing the evaporator. I put a gauge on and got the readings below. Can anyone tell me if this is somewhat normal, low, etc? I will, as advised check the AC compressor when it is happening. It's been a challenge with my son away at school.
Light Motor vehicle Gas Gauge Machine
 
#9 ·
Ok, I feel like this will end with me pulling the dash out and replacing the evaporator.
I can't tell you for certain what you're looking at, but I can tell you that 99% of the AC problems on this forum end up that way.
 
#13 ·
I am back on this. Here is the gauge with the AC and car running for about 10 minutes.
The scenario is still AC seems to work fine until he drives it for at least 20min or so. Then it blows less air and the reduced airflow is not cold.
I would think about tearing straight into the evaporator core but with it being a 17 and manufacture date of 1/17, I am not 100% convinced that is it.
The low side pressure has me scratching my head?
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#16 ·
Looks and sounds like a possible low refrigerant issue. The low pressure is puzzling. But when your idling you will not move refrigerant as fast in system which keeps compressor running. Also low refrigerant can cause freezing in evaporator which allows less airflow. Need to figure out why you have higher low pressure than the high side
 
#17 ·
Does anyone know where the Evaporator Temperature Sensor is located?
I took the car to an Indy I trust. They evacuated the system and reloaded it. They said it was slightly low but not much at all. They pulled codes to see if they could find anything there and couldn't find anything. From the digging they did and data they could pull, they think that possibly this sensor is not reading correctly causing it to ice up after the 20+ minute drives as we have experienced. My guess is this would still require a trip into the dash?
I will keep everyone updated.
 
#18 ·
I got to see the computer data from the evap temp sensor at the indy. That is the issue.
With the luck everyone has with these evap cores, I imagine I will change the whole thing to be safe. I do see a part number for just the sensor and was wondering if anyone has ever been able to get to it without removing the whole dash?
 
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