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I'm doing SCIENCE!
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Discussion Starter #1
Just got back from an extended vacation (vacation + family member going into the hospital, so I stuck around). Had a lot of fun with the truck on the trip, hauled some logs, drove some back woods trails, climbed a couple of tailing piles from old mines. Good stuff.

The morning I went to leave at the start of my trip, my AC wasn't working. Thankfully the dealer diagnosed it as the High Pressure sensor, replaced it, and everything seemed fine while I was up in Michigan. AC worked great, when I used it (gotta love the UP weather, 80s is a 'hot' high, most of the days were low 70s and nights in the 50s).

On the way home, however, I ran into some trouble somewhere in Georgia. Humidity had been going up as I headed south, and the truck started to get a little warm. I noticed that even though the fan was set to the 4th setting, hardly any air was coming out of the vents (the blower WAS running). Turning it to full didn't help much, other than making the blower louder. After flipping it back and forth a few times, I turned the AC off and switched to heat to see if that worked. Nope, still hardly any air coming out of the vents. After about 15 seconds, though, the amount of air started to increase until, after about 45 seconds, it was really blowing. I turned the AC back on and everything was fine...

For about 2.5 hours, at which point the amount of air coming out of the vents started to drop off.

The hell is going on? Is the heat exchanger in the dash icing over and blocking the air flow? Is that even possible? I thought when an AC unit iced over, it was the condenser coil that did so, not the heat exchanger?
 

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It's the evaporator, under the dash, that freezes up. Not normally a problem on later models unless you are running for an extended period of time in "Recirc" mode.
 

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I'm doing SCIENCE!
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Discussion Starter #3
It's the evaporator, under the dash, that freezes up. Not normally a problem on later models unless you are running for an extended period of time in "Recirc" mode.
Ah, that makes sense, because this was around hour 14 of my drive, and it was in Recirc.
 

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Sounds very similar to the other guy with the same description, fan speed slows and speeds up.

Also, curse words are not allowed in forum titles.
 

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I'm doing SCIENCE!
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487 Posts
Discussion Starter #6
Re: What the heck, AC?

Does your HVAC controls bind or don't go from complete left or right?
There's a known issue with a gear that pops out causing the AC/Heat not to fully function. This is located behind the right rear of your radio.
Nope, they operate smoothly.


Sounds very similar to the other guy with the same description, fan speed slows and speeds up.

Also, curse words are not allowed in forum titles.
Fan speed is constant, at least judging by the noise the fan is making, but air flow is not. I'm going to go with the 'icing up' idea, as that fits the symptoms pretty well. Especially the part about turning the heat on for 45 seconds or so solving the problem (man, the heater in this truck can crank).

Also, sorry about that, didn't realize that 'hell' was considered a curse word. :ugh:
 

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Normally, when it freezes up like that, it's because your freon level is low. I'd bring it back to the dealer that changed the switch and have them check the freon level.
 
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