Cabin air problem-not blowing

[mb311]

2011 Chevy Tahoe LT.

Unfortunately my problem does not seem common enough to find a an answer on google for a Tahoe or Silverado of like year. Got a few ideas of possible culprits.

Symptoms- After running the a/c for awhile (1 hour +) air flow diminishes on all cabin vents over about 5 minutes until air flow stops completely. This occurs on a/c, heat, and cycling all the options for floor, dash, defrost, etc. The blower motor is positively still running. Just sounds louder like there is a blockage. After sitting for 30 minutes or so, things are back to normal function. I took the underdash cover off and noticed some moisture on the box just left of the blower motor-is this normal? The floor panel is not wet though so probably not a heater core issue.

My understanding is no cabin air filter in these to get clogged up?

Seems like something maybe freezing up? Thawing after resting a bit allowing things to function normal again? Possibly the reason for the condensation under the dash?

But what could be the cause?

For whatever it may be worth, a couple weeks back my a/c was not blowing very cold, but no lack of air flow. We had it serviced and it was a bit low on refrigerant. This was refilled and we had normal function for about a week before this problem popped up. Or possibly we just did not drive it long enough for it to show itself.

Also a couple times air, looking like steam almost has come out of the vents.

Thanks for reading and offering any advice.

 

[Doubeleive]

weird, does it only do this while on a/c? , so lets say you put the temp on a neutral setting does it still do the same thing? or with heat?, if it does then I would suspect the control unit (dash control). they run about $160 on rockauto. otherwise no idea and would probably take a more in depth diagnosis by the dealer or a shop that is capable.

 

[mb311]

weird, does it only do this while on a/c? , so lets say you put the temp on a neutral setting does it still do the same thing? or with heat?, if it does then I would suspect the control unit (dash control). they run about $160 on rockauto. otherwise no idea and would probably take a more in depth diagnosis by the dealer or a shop that is capable.

Once it stops working the heater shows same lack of airflow. A short restabout 20 30 minutes and back to normal.

 

[swathdiver]

Low freon can cause this. There may also be a malfunctioning actuator or broken door. Right, unless someone put one in, there is no cabin filter.

GMs Tech2 scan tool can see everything going on that you cannot, any internal BCM codes, test and see what the actuators are doing, check the high and low pressures and much more. Where do you live? Maybe someone on here lives nearby and has one?

 

[Doubeleive]

Once it stops working the heater shows same lack of airflow. A short restabout 20 30 minutes and back to normal.

I understand that but my question is does it also do this if you are running just the heater for the same period of time?, or does seem to be only AC related?

 

[mb311]

I understand that but my question is does it also do this if you are running just the heater for the same period of time?, or does seem to be only AC related?

Can't say. Running heat for an hour when it is 95 degrees could be a health hazard

 

[Doubeleive]

Can't say. Running heat for an hour when it is 95 degrees could be a health hazard

lol, well I think for testing purposes it could be done at idle with the windows down, I don't know what else to suggest apart from paying to have it done, maybe take it back to whoever did the ac service and see what they say. maybe it has a leak and it's causing a problem.

 

[gpracer1]

WHEN this happens is the blower on high or low? If you live in a humid area and use low blower you get close to freezing the moisture. Your system should cycle the low side to prevent this. It may be not cycling correctly or low on refrigerant causing partial then total freeze.

Next time it does this turn off the AC button only and keep the blower on high. If you do this parked you should see some water running out the passenger side on the ground.....that’s the ice block melting.
What fan speed does this happen at? My guess low.

 

[mb311]

WHEN this happens is the blower on high or low? If you live in a humid area and use low blower you get close to freezing the moisture. Your system should cycle the low side to prevent this. It may be not cycling correctly or low on refrigerant causing partial then total freeze.

Next time it does this turn off the AC button only and keep the blower on high. If you do this parked you should see some water running out the passenger side on the ground.....that’s the ice block melting.
What fan speed does this happen at? My guess low.

I have been noticing a larger puddle of water on the garage floor after parking it. So this makes sense. I did notice some similar symptoms on other vehicles in a google search being a faulty pressure control switch. Maybe a possibility? Looks like a cheap thing to try at about $25 for the part. I'm thinking first step is to take it back in and verify system pressures are correct and go from there. Seems too coincidental to have them fill a low system and suddenly have this problem pop up.

 

[jmm121783]

sounds like it could be freezing up and preventing airflow, which in turn is straining the blower motor making the sound.

Doubleleive is right, you can easily narrow the problem down to this if when running the heat there are no issues.