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Usually, after 40-50 minutes of driving, AC starts to blow at a lower speed. It's still cold and set on high but air barely comes through the vents. It feels like there is condensation somewhere which doesn't let the air to go through. I hear that the blower is blowing hard but the air just doesn't come out through the vents. It gets stuck somewhere on the way

If I keep the car off for an hour and start driving again, AC will work for another 40-50min before the issue repeats.

Trying to figure out how to fix it. Thanks!

 
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Perhaps the blower or cabin filter are clogged with dry material normally, and when the ac is on it becomes damp and clogs.

pull the blower motor out and inspect it.

 
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I have removed the blower and cabin filter. They don't look like they are clogged with dry materials. Looks like normal use. I have taken a couple pictures of how the blower and cabin filter looks like http://imgur.com/a/nwR0FJD Any other suggestions what to check?

 
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need more details to see what you're dealing with

Does the blower fan motor speed slow down?

Or does only the airflow velocity at the vents decrease,but the fan still sounds like it's running full blast?

airflow obstruction, .....Maybe you'd notice the air from the vents was so cold for a while the evaporator core literally became a giant ice cube

If the evaporator core froze up and you parked long enough for the ice to melt and go out the drain tube
some people notice a "much bigger than normal" size puddle of water under the car.



If the motor speed slows down .
(I hope most people can listen and judge a big change in the fan speed, based on changes in sound/pitch )
easy simple and fast check:
reach under the dash and smack the bottom of the motor with ......the palm of your hand..... (If equipped with an underdash cover, I aim where the blower motor is supposed to be located)
If you can make the speed change or make a stalled motor spin again, that motor is usually bad. (I say usually because it's not always. Consider the general vicinity of you hitting under the dash.... something like an electrical connection or contact problem might get better or worse because of movement and vibrations from hitting as well)

If that's not the problem, i might wiggle wires and connectors hoping for easy to find connection problems.
If nothing obviously wrong there, i grumble and refill my cuppa coffee, and open up my toolbox

 
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Thanks for the reply ezone!

It doesn't. I can hear that the fan motor speed is still high.

I can confirm that airflow velocity decrease but the fan still sounds like it's running full blast.

What could be the issue? My guess is that when I run AC for 30+ minutes something freezes up and obstructs the airflow. It makes sense that let's say ice melts down and AC works again after the car was turned off for an hour.

How can I figure out what is obstructing the airflow?

If the evaporator core becomes a giant ice cube can I see it when I open the hood or do I need to get under the car? And if that is the issue what would be the solution?

 
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Still haven't figured out the issue (sad)

 
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The evaporator core becomes coated in ice....simply because the core is too cold. That's going to be the airflow obstruction.
Core is inside hvac system case , all hidden by the dashboard. You can't see or touch without a lot of work, and there's no reason to pull it out to SEE if its a big ice cube...because your careful observations and descriptions are a flashng neon arrow lol

that answer only determines the next questions anyway

bill nye stuff here first...
humid air + cold surface = water droplets (condensation),
water freezes at 32F.... The core must always stay above 32F .
. This system regulates core temp via cycling the compressor before it gets that cold
The evaporator core has a temperature sensor stuck inbetween a couple of fins.
The control unit uses that temperature data to decide when the compressor needs to be turned off and on so the core temp stays above freezing..

generic example, the core won't freeze if the compressor is turned off@ 35F, on@ 37 or 38F ...(air temp at the dash vents is rarely as cold as the evaporator core temp, but a fast acting digital thermometer in the vents should rise and fall a few degrees pretty quick whenever the compressor cycles
The compressor could run all day continuously if necessary on a hot day/high heat load, but the compressor must always cycle off when the core temp spec is reached




tl;dr
the core is too cold.
Compressor was supposed to cycle off before the core got cold enough to freeze water....and cycle the compressor off and on as needed to maintain core temp within a few degree range , but always above freezing..

Sooooo.....
Does the compressor cycle off/on at the correct temps?
Does cycle off/on at the WRONG temps?
Does the compressor ever cycle at all? (running continuously)

consistent or repeeatable problem? or intermittent problem?
(problem definitely happens every time you drive that certain route or maybe specific time and seed conditions...
...or is it more random, dont know when it may or may not act up even though its your same daily commute ,


We KNOW the ac gets cold, that tells me the freon is ok.

 
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My daily commute is 2 miles so it happens only when I go on longer trips. I always have this issue after 30-40mins of driving with AC on so it is repeatable problem.

How could I check these things? Should I hear if the compressor is engaged all the time?
Should I try to turn off the AC and see if the compressor is still engaged?

Is there something I could buy, easily replace like a fuse to see if it helps? Or is it directly a compressor issue and I will need to get a new one? (This is the new compressor. I have changed it two years ago but I don't recall when this issue has started because usually I don't drive that long)

 
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Two years later still having this issue :| any suggestions?

 
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Might be over/underfilled, might have moisture in the system, better off taking it to the dealer or a shop that specializes in AC repair.

 
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After reading for some more threads on google think it might be AC relay (39794-SDA-A05). It costs 9.99 for two on amazon so will see if that helps. From my understanding clutch is engaged all the time which makes the whole system freeze and then air can't flow.

 
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Potentially, let us know the results

 
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You should be able to tell if the compressor is cycling as it should.

 
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So I can't believe it took 2 years to fix it but today is finally the day my problem with AC is over. It wasn't bothering me too much because I rarely drive over 30min. The AC control unit was sending the signal to keep AC on ALL THE TIME which means the compressor wasn't cycling and after an average of 32min driving system would get icy and would still blow air but ice would block it, so it means AC compressor would keep working. I have replaced the AC control unit which I got from eBay for $70.04 and then I noticed that the AC clutch would engage and disengage when AC is on/off (fixed the issue regards cycling) Great youtube video on it
But lately, sometimes AC wouldn't work at all, AC clutch wouldn't engage but then would engage after some time of driving so I knew AC clutch magnet wore off so I needed new magnet but none of the shops wanted to replace magnet because it was more work than replacing the compressor and probably they didn't want touch such a small job. So got a new OEM Denso 471-7054 A/C Compressor for $243.37, the shop replaced it for $220.

So total of $70.04 + $220 + $243.37 = $533.41 later I have now working AC.

 
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Okay, I thought I won't have any more problems with AC but something weird is happening.

It's winter now so I use a heater instead of an A/C but I can hear that the AC clutch is cycling while AC is off and only the heater is on.

Is my replaced AC control has some electrical issues? Is it an ECU issue? Any ideas?

 
Rep Power: 223

The car will run the compressor to help pull moisture out. This is normal.