My 2017 Tahoe's air conditioner had very restricted airflow about 2 hours into a 3 hour drive (almost no air coming through front vents with fan on high). Turned AC off and it improved the airflow within about 5 minutes. I assume the evaporator was froze up. I have not driven over an hour since then but the AC seems to be working fine, only had that issue the one time. I put a thermometer in a vent and it's blowing 40 degrees. Seems to be ok but this is a used vehicle I recently purchased that has a 4,000 mile warranty. So I'd like to figure out if there's an issue asap.

Any advice is greatly appreciated.

My 2018 Chevy truck has a cabin air filter that will reduce air flow when it needs to be changed. I usually replace it and the engine air filter every couple years and I get both of the fram filters at Walmart. Iirc, a simple torx head screwdriver is needed to replace the cab filter which is behind the glove box and easy to change.

Following.

Our 2015 Yukon XL started doing the exact same thing last summer, then I was able to ignore it all winter. Now that it's AC season again I realized that the problem is still there. Same symptoms. With AC on, airflow gradually diminishes down to nothing, doesn't matter how high you turn up the blower. Turn AC off via dash switch (but keeping blower running) seems to unfreeze it very quick and then you're good to run the AC again for 10-15 minutes before the cycle repeats. I've also noticed larger than normal puddles of condensate drainage when parking after a long drive (so it doesn't appear that the drain tube is blocked... there's just more of it).

Things I've tried / investigated so far:

- Cabin air filter (the one that you have to disassemble the glove box to get to) - changed it out with a new filter - no improvement (is there another filter somewhere else?)
- Checked refrigerant charge with manifold gauges (thinking it might be low) - charge level right where it should be and can't see any signs of leaks anywhere

Some online investigation leads me down a path of possibly a faulty evaporator temp sensor. Logic is, if the sensor fails then it may not register when the evaporator has cooled to the point where the compressor should be cycled off, so it keeps running full bore until you have a frozen coil.

I ordered a new sensor but it looks like you have to take the dash completely apart to get to it. Have been putting the job off for that reason. Any other suggestions?

Is the drain clogged?

Plenty of drip from both front and rear evaporators. I did just change the cabin air filter. Old one was clean but appeared to be a thicker filter than the Delco replacement filter.

Might need to hit the evap coil with a cleaner. Some are hard to reach but they make spray foaming cleaners that might work.

I have to do the same with my old Nissan. I just turn off the ac button (turns off compressor) but leave the fan on and it blows air through the evap and melts off the frost. Then when the air temp starts to go up at the vents I know it is thawed and I put the AC button to on again.

In my many years, I have found that one of these four things causes your issue

1. Refrigerant is the lifeblood of your car's air conditioning system. It's a liquid that's pumped through the system to cool the air, and it's essential for the AC to function properly. However, if the refrigerant level is low, the system can freeze up.

2. Clogged air filters can cause your car AC to freeze up by restricting airflow

3. The expansion valve is responsible for regulating the flow of refrigerant through the system. If the valve is faulty, it can cause the system to freeze up.

4. The thermostat is responsible for regulating the temperature of the system. If the thermostat is faulty, it can cause the system to freeze up. This is because the thermostat is not able to regulate the temperature properly, causing the system to overheat and freeze.

Went ahead and put it in the shop. They found a leak in evaporator core. Hoping that takes care of it. Thanks for the help.

George08 said:

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Went ahead and put it in the shop. They found a leak in evaporator core. Hoping that takes care of it. Thanks for the help.

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You're gonna love the bill.


If it's like our 2017 Silverado the AC Condensor also is the transmission cooler. And it is filled with the new, expensive, and not as good, R1234.


I would also suggest having the transmission cooler thermostat checked/replaced or just bypassed. That thermostat is a leading cause of death of the 6 speed transmissions. It gets stuck closed and will not cool anything. Happened to us while pulling a trailer. Ours is now bypassed on recommendation of Oliver Bros transmission who put in our rebuilt transmission at 70k miles.