HVAC issues - air isn't blowing from ANY location

[TexasAggie]

Ran into an odd issue last weekend while on a 300 mile trip. Started out everything was good, then I noticed that the air coming from the vents (was running AC as it was warm outside) was coming out very slowly. I start paying attention and after another 10 minutes it wasn't coming out at all. I increased the fan speed and could hear the fan and air moving, but nothing out of the vents. Tried the floor and defrost as well, and still nothing. We stopped for lunch an hour later and I messed with it a bit. After the truck sat for 10 minutes, I turned the key and everything was back to normal. We resumed the trip and after about 20 minutes the same thing happened - slow loss of air. The cycle repeated itself each time I stopped.

I'm thinking this is an issue with the mode door actuator on the driver's side of dash. Anyone have a part number or a good way to test this?

 

[evilunclegrimace]

Year,Make Model?
Stick you head under there and watch what it does.

 

[someotherguy]

Sounds like your evaporator core froze over. All air in the system regardless of setting must pass through it, even if the A/C is off, or you have the temperature selector all the way to full hot.

Next time this happens, turn the A/C button OFF. Leave the fan on. As the ice melts, you'll start to regain some airflow, and it will still be cold as it's passing over ice. After several minutes it should melt completely and the air will be warm. Turn the A/C back on.

Likely a marginally low refrigerant charge or partially clogged evaporator core fins that are more prone to freezing up because condensation collects on the debris which is impeding airflow.

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See the airflow path from the blower motor on the right - passes through the evaporator core before it can go anywhere else in the system. The flap you see to the left is the temperature mix control.

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Richard

 

[movietvet]

The problem will be one of the two causes that have been suggested.

The other problem is the lack of vehicle info. Is it a secret?

 

[caw_86]

Usually its the lack of airflow that leads to a frozen coil

 

[evilunclegrimace]

The problem will be one of the two causes that have been suggested.

The other problem is the lack of vehicle info. Is it a secret?

Why yes,yes it is.

 

[TexasAggie]

My apologies, I got sidetracked when writing the original post and forgot to add vehicle info when I came back to it.

1999 K2500 Suburban

 

[TexasAggie]

I'll check freon level and see what it is showing. Radiator and condenser are both clean and clear, so should be flowing fine. What's the best way to check the evaporator to see if it is in fact freezing over?

 

[454cid]

I'll check freon level and see what it is showing. Radiator and condenser are both clean and clear, so should be flowing fine. What's the best way to check the evaporator to see if it is in fact freezing over?

You could pull the blower motor out, and it's around the corner. It would be good to get in there and remove any pine needles or Taco Bell bags, any way

 

[movietvet]

I'll check freon level and see what it is showing. Radiator and condenser are both clean and clear, so should be flowing fine. What's the best way to check the evaporator to see if it is in fact freezing over?

@someotherguy gave you your answer on how to check if the evaporator is freezing over. When the problem starts, turn the a/c off and leave the air on and see if the flow gets back to normal, after the evaporator thaws. You can also attach gauges at the a/c and see where the pressures read and if you do that and post the pressures here, will need to know what the ambient temp is at that time of the pressures reading. BUT, if is clogged with lots of debris in front of it, that is a whole other can of worms.