And herein lies the great value of such forums. Where else would you likely hear of the solution? Not likely the manufacturer as it is one they would be responsible for. But one has to wonder, with the popularity of this planner why is this seldom reported? I recently read a posting about the differences in shop vacs and central dust collectors whereas shop vacs are high volume high velocity systems and central dust collection is high volume low velocity. Keep in mind this brain has a few years on it and I can't locate that post/article. Could this be a factor?
Another consideration, if this just started 2 years ago something must have changed. Was it the method of dust collection, a change in design (add/remove piping blast gates, length of run). Has using a shop vac been tried? I mean this worked fine for 8 years so something had to happen, right? Another thing to keep in mind, fan blades move air but dirty fan blades move much less air. In my years as a HAVC tech I had to work with a number of engineers due to design build projects. That meant getting down and dirty with the specs especially with projects like clean rooms. Most of us never look or have access to the design specs of a piece of equipment but that's where the information is about air volume and static pressures.
And that's where things can go awry. If the fan is accessible I'd first clean the blades. It would be helpful to check the RPMs but that spec may not be listed on the fan but amp draw might and that, when checked in the installed position should be doable easily if you have a clamp on meter that reads amps and it wouldn't be a clamp on if it couldn't
But then is it DC or AC amps?
Or again, if the fan isn't too expensive try replacing the fan but that's a gamble because it may well not make a difference. Also checking the path all the way to the exit and making sure it's unobstructed and reasonably clean. This could take some time if you truly want to determine the issue. The process that the one fella did removing the impeller (fan blade) may have improved the outcome but may have masked the true reason for the problem.
And this is one reason I have grey, balding hair. It's sort of like finding a blown fuses/tripped breaker on a HVAC system. Some, not so good techs simply replace the fuses or reset the breaker, turn the system on and if it runs consider it fixed. A better tech checks a few things like amp draw on the system. A good tech puts the system through it's paces. Let's say it's a heat pump. Turning it on puts it in one mode, either heat or cool. So maybe it runs fine in both but there's one mode that hasn't been checked. Defrost uses several circuits that aren't in play during a normal heat mode run. And not checking that can keep you coming back on return calls, more fuses, and on the house labor for not curing the issue the first time.
Long story shorter, it was the defrost thermostat lead that was tie strapped at the factory on the discharge line of the compressor. After about 15 years of not being a problem it became a problem when the wire shielding finally rubbed through to the copper wire thus creating a direct short when the defrost sensor made (the line got cold enough to close the contact in the defrost sensor thus allowing 24 volts to travel through the wire). This created the short that blue the 3.2 amp fuse that GE used in their control system and is somewhat unique in that it has the cap and fuse as a single part.
For the record I was the second tech on this call. The first simply replaced the fuse and started the unit and walked away. He was on site for less then 15 minutes whereas I was there almost 2 hours. Finding the problem in defrost was done in probably the first 45 minutes. Locating a wire worn through and shorting out was a bit harder........
Just saying, it's not always what it appears. I would look deeper but I'm old and have time.....not sure how much time but some.......