[Wakko]

When the air conditioning is operating normally, after anywhere from 5-10 minutes, the air stops coming out of ANY of the vents. Turn the fan on high and you'll hear air trying to blow under the right side of the dash, but it's obstructed. Turn the snowflake off, and the door will slowly open, allowing air to pass through the vents again. Turn the snowflake on, and eventually it closes again.

It sounds to me like one of the actuators, and I saw the photo of the underside of the dash and it looked like there were four of them in there. Is this the case? Any opinions on if this is going to be my problem?

 

[Rambodog]

Sounds to me like you have a blockage alright, but in ice form. When an A/C system is low on refrigerant it can make the evap coil freeze. This happens because of the relationship between pressure and temp. The lower pressure causes the refrigerant to enter the evap at a temp below freezing. This causes the condensate that would normally drip off the coil to freeze and eventually block air flow. Once the A/C is turned off, the ice melts and air can again pass through.

 

[Wakko]

Interesting theory. If this was the case, how long would it take for the ice to melt? Once I turn the cooling off, the door opens in about 15 seconds.

 

[Rambodog]

Interesting theory. If this was the case, how long would it take for the ice to melt? Once I turn the cooling off, the door opens in about 15 seconds.

There are too many variables to predict that. It depends on how much ice and air temp and amount of flo at the coil. There isn't a guaranty that it's the problem, but going by the symptom you explain, it fits the bill well. Since most folks are not running around with a gauge manifold to read pressures, you could buy a cheap bottle of 134a and when connected you can see if level is low on the dummy gauge the cans have on top to get you in the ball park for level correction. If your low, adding should stop the symptom your having till it leaks back out of course. A quick dirty and cheap verification anyway.

 

[Wakko]

I just had it topped off a few weeks ago after being completely empty. He added sealer, and it appears to have been holding a charge, but I'll go by and have him check it out.

 

[Wakko]

Update in case someone else has this problem at some point:

When I got my truck, a couple of the A/C buttons were worn, so I replaced the controls with a NOS unit. It worked without any programming. The old controls did not show outside temperature, but the new ones did. The dealer did work on the truck after the install, and I asked them to verify any computer issues, including the controls. They said that they did.

My truck has a gremlin check engine light that the dealer couldn't fix in addition to the A/C issues. Brought the truck to the local mechanic, and he showed me a laundry list of codes that the truck was spitting out, showed the computer saying that it needed certain modules updated, and suggested a flash/reprogram of the entire truck. I went ahead with it and VOILA...all is fixed. The outside temperature is gone from the controls, I get no blend door closure, and my check engine light is staying off. I had also lost only 1/2 ounce of freon in the time that he had refilled it, so I'm content with that too.

All in all, a successful repair of something not-so-obvious.