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DanDweller

No AC after Carwash

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After going through an automatic carwash, the AC is blowing, but not cold air.  Any idea what is getting wet?  Last time this happened, it started working again a few hours later.  (TC, 2015, XL, LWB)

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The only part under your hood exposed to water from rainfall or a carwash is the front grille fascia.  Water would have to spray directly in for anything to get wet.  The only part on the front of the car exposed would be the air conditioning condenser, accumulator, fittings, and lines.  This is the part that looks like a radiator, in front of your radiator.  The air conditioning compressor is under the hood in the engine bay.  Look for visible damage.  

 

Full Size Assembly Image

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I would be suspicious of a connection getting wet, maybe belt for compressor getting wet and slipping but Id be surprised at that.

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May have a damaged condenser.  Rock strikes.  Bird strikes.  Animal damage.  But probably not a line leak or bad fitting.

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It's possible the outside ambient air temperature sensor is getting wet in the car wash. They are often located up front near or under the front bumper for airflow, and cold water can drop the temperature reading below the expected parameters which the computer will see as a sanity malfunction and switch off the compressor to protect it. Once the sensor warms back up the computer restarts the compressor. I've seen this happen on other vehicles, but not Ford. But it's entirely plausible scenario.

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Very good point about the ambient air temperature sensor.  Sensor also has wiring and a connector which could get wet.  

 

In most cases, if there is damage and/or a leak, it would be consistent.  Not just after going through a car wash.  You probably won't find a leak with a visual inspection or tracer dye.  There very well may be water wetting a bad electrical connection.  No reason why water is getting under the hood.  Even if you go through a car wash which sprays water upward, there is an underbody shield.  I can only imagine water spraying in past the passenger side wheel well, towards the side of the engine where the belts and pulleys are.  

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On 6/23/2019 at 12:36 PM, Don Ridley said:

Does the windshield leak? 

Not that I know of.

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On 6/23/2019 at 11:37 PM, Fifty150 said:

Very good point about the ambient air temperature sensor.  Sensor also has wiring and a connector which could get wet.  

 

In most cases, if there is damage and/or a leak, it would be consistent.  Not just after going through a car wash.  You probably won't find a leak with a visual inspection or tracer dye.  There very well may be water wetting a bad electrical connection.  No reason why water is getting under the hood.  Even if you go through a car wash which sprays water upward, there is an underbody shield.  I can only imagine water spraying in past the passenger side wheel well, towards the side of the engine where the belts and pulleys are.  

I did notice this plastic shield beside the rqdiator (driver side) is busted. 

20190625_202148.jpg

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Good find on the plastic shield. Looking at the sensor location, it is up front next to the condenser. But which side is a little murky. This photo from the service manual shows it, but on the big photo it looks like it's on the left, the smaller (upper left) picture in a picture shows it on the right.... Update - Just looked at my 2017 - it is on the left. You can see yours in your photo just below the middle strake of the fascia. That's a great place to start, considering there is damage in that area.

 

In any case, you have intermittent a/c operation, which indicates a more likely electrical or sensor issue. If there was a leak in the refrigerant portion of the system, it would stop working and not come back on until repaired. Unfortunately you will need to catch it in the non working state and do some diagnosis, pull codes from the computer that will point you in the right direction to continue diagnosis and find the cause. Replacing the sensor proactively is easy, but with hit or miss results.  All outside connectors are water proof, and generally do a good job of keeping moisture out, but since there is damage there, it may have damaged the connector or sensor, which would explain intermittent operation. You may want to pull the undercover and take a good look.

 

 

 

 

AAT.JPG

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I would get a piece of plastic, epoxy it in place to protect the sensor, and the problem is solved.  Sensor works fine when dry.  Keep it dry.  Nobody will see that patch job.  Or you can find a replacement front grille fascia, and change it out to a new part. It's probably an entire new front end piece, bumper cover, grille, all I 1 body part.  

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Actually that plastic piece is behind the sensor, it doesn't do anything to protect it. The sensor needs airflow to work properly, which is why it is up front and in the vent area. It just needs a good visual inspection to see of there is any damage.

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Have you run a scan on the AC system? That could tell you a lot.

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