A/C strange behavior

Car is a 99' A6 2.8 Q with only 25K miles. The A/C, every now and then, would blow warmer than expected cold air; one time going through a car wash I put trans in "N" neutral and the air temp went totally warm as if A/C is
not running at all. In all these cases if I put the recirculation on the temp returns to cold almost immediately.
I don't think this is a refrigerant issue but maybe an air gate or (less probable) belt issue.
Any help here is welcome
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In my '98 A6Q (wagon) I had a similar problem. Identical actually, except that I never played with the recirculation button to see if that would have any effect. My problem turned out to be a bad water temp sensor. The computer would get a high reading from this bad sensor and think that the engine was overheating and would cut out the A/C to give the engine a break.
I cannot recall now if the water temp guage indicated that the engine was overheating. Maybe not, as I think that the 2.8 engine has more than one water temp sensor.
I'd guess that this is not your problem as I do not see how the recirculation button would cause the A/C to kick back in if it were. But, I contribute it for whatever it might be worth.
Good Luck, Bob

wash
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