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Discussion Starter #1
During a recent roadtrip in our 2010 EXL, we noticed an AC issue that only occurs after driving for about 30-45 minutes. Summer in Florida means it is hot and humid so the AC is always on. At the start of the trip, everything was working fine and both front and rear are blowing cold. But after 30-45 minutes, the air from the front vents goes from cold to cool and the rate of airflow reduces significantly despite turning the blower up to the highest setting. The rear AC seems unaffected and was still blowing cold at full speed. If we would shut off and leave the car for about 10 minutes, the air would start working again for the next 30 minutes or so and then the same reduced airflow would occur.

First I suspected the mode motor since that has caused me issues before, but I verified the position of the dampers was correct and disconnected the mode motor to eliminate that possible issue. Also I inspected the cabin filter which was clean (recently changed). But those didn't seem to make a difference. So during the return leg of our trip after the problem occurred again, I turned the compressor off using the AC on/off button and after a few minutes the rate of airflow from the front vents increased despite the blower still being on the highest setting. I also noted the sound of ice falling from within the dash. During the rest of the trip, I kept cycling the compressor off when the airflow would decrease and then back on for about 15-20 minutes and it would cool just fine until the airflow slowed again. Later in the trip, I noticed that small drops of water were coming from the center vent on the passenger side. I suppose that was moisture from the iced up coil getting blown through the vents. I checked under the car and there was a good steady drip from both the front and rear coils so the drain valves seem fine. After returning home, we've used the car around town on short tips and have not had the issue return.

So it seems something is causing my front evap coil to ice up after long periods of use. First thought would be low refrigerant but since the rear evap coil worked fine it doesn't seem like the system would be low. Perhaps the front expansion valve or front coil temp sensor are the issue.

Anyone has this icing issue with the front coil?
 

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I suspect the common a/c relay problem. The relay fails and your compressor will never turn off. I would replace that as soon as possible. You can get it at autozone or any parts store.

Sent from my SM-N950U using Tapatalk
 

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Discussion Starter #3
Thanks for the response. I should have mentioned that I replaced that relay a couple of years ago as preventative maintenance. And while troubleshooting this issue, I did observe the compressor cycling on and off when called for so the relay doesn't appear to be stuck.
 

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Discussion Starter #4
Ended up getting the expansion valve replaced which is pretty extensive since you have to get to the evap coil up in the dash. Took to local mechanic since it is beyond my DIY abilities to deal with refrigerant. The mechanic noted that the refrigerant was not low but the high and low pressures were a little wonky. I don't recall the values he shared - should have written them down.

For about $650 they replaced the expansion valve, vacuumed and recharged system, replaced dryer and thermistor. Thermistor may not have been the issue but it is only a $20 part and easily accessible on driver side. Been working great on two roadtrips since then.

I also paid extra for the mechanic to replace the mode and driver mix motors that were acting up previously but not the cause of this issue. For those, only paid for the parts (about $250) since they were already up in there doing the expansion valve.
 
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