Interesting AC Problem (To Me)

[rugger33]

I have posted a description of this problem before (with no solutions found) but as it appears to be worsening, figured I would post again. I am in South Florida so even though it is fall, it is worth trying to figure out down here.

AC runs cold, compressor kicks on and seems to run normally. On short trips. On longer trips, at almost exactly 45 minutes in, the blower mower slows to a crawl and basically quits blowing cold air (doesn't blow at all). A small whine from that general vacinity can be heard at the time. First thought, it's the blower motor. However, at that 45 minute mark, I turn the AC compressor off, and about 1 minute later, blower motor "releases" and blows air (which is still cold for a bit on recirculate). I then turn the compressor back on after a few minutes and repeat the cycle.

This has been going on for about 3 years but seems to be worsening now. I just replaced the coolant and bled the system in case there was an air mixture issue (as in some grease monkey not properly bleeding the heater valve in a prior change (not that there's anything wrong with grease monkeys)) but I am stumped . Any suggestions LSers?

 

[joegr]

You almost have the symptoms of the evaporator freezing up. That would be due to a defective expansion valve. (You say it blows cold, so I assume that the refrigerant level is okay.) However, if it was the evaporator freezing up, then it should take several minutes to thaw it out, not just one.
The next 45+ minute trip that you take, select recycle at the start and leave it there. If it now doesn't freeze up or takes a good bit longer to, then it would seem that it is indeed freezing up. (Setting the control to recycle reduces the amount of moisture that the system has to deal with.)