I noticed during my 3,000 mile plus road trip during the past two weeks in the '92 Jeep Cherokee XJ 2WD that, after some time on the highway, the blower slows down almost to a stop and then speeds up again. Goes on like that all day long. And this happens without me even touching any of the A/C or heater controls. Now that is weird.

 

Is it slowing down or changing position? Dash/defrost? I thought mine was slowing down when I accelerated thinking bad alternator, but I had a broken vacuum line that controls the position and under acceleration it was losing vacuum and swapping to defrost.

 

I never thought about the change of outlet direction due to a vacuum problem. I will have to look into that possibility! Thank you.

 

Neither did I. When I had the problem the cause was electrical and my thinking stopped there. I'll add it to the smart book.