PLEASE HELP!

We have a 2008 Chrysler Pacifica. It has been a great car for past 4 years. No problems until now. The air conditioner blower motor started making a weird sound like an old box fan. We were on a long trip about 2 hours had passed and the air flow completely stopped in front. The rear fans kept blowing. After a few minutes it came back. This has happened a few times. Took it to local mechanic. He changed air filter under dash and blower resistor. The sound came back next day. He took blower motor out and ran it. It did not make sound. He checked the blower motor area and all was clear. IT GET WEIRDER. Now when I turn right, the blower seems to get a power surge. When I turn left, it does down. This only happens when car is in motion. Mechanic said he hooked computer up and alternator was bouncing from high to low. Replaced alternator! Problem still happening!! And the air flow stopped again after 2 hours of driving. I turned it off, gave it a minute, turned back on an it worked.
Any help would be greatly appreciated. The Chrysler people have no clue.
Thank you,
Mike

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