Sure sounds a lot like the ACC control board needs to be resoldered. The solder joints for the pins will develop small cracks, cold solder joints, and then the fan begins to act up.
There are plenty of threads on that one here. You can buy a rebuilt of course, but why not DIY?
When I soldered mine I noticed there were several bad spots, they don't show without looking very closely, but they are there. I used some electical contact cleaner to clean the contacts.
So far it has worked flawlessly. Did the job last summer. Took about an hour to remove/ reinstall the unit, and about two hours to do the soldering.
I did read that there is a temp controlled Weller soldering iron available. That would be a real help for this job.