I have a 2.5 with the snow dam but even that does not keep leaves from getting up into the fan cage and lodged in the squirrel fan.
Once leaves are in there, the fan becomes unbalanced and causes significant vibrations when spinning rapidly. Not only is it annoying and noisy, my concern is that an unbalanced fan will cause premature fan bearing failure.
Tesla during the annual service would clean it out but leaves seemed to get back up in the fan fairly quickly after being cleaned out. So, I decided that I would try to fashion something to keep the leaves from getting in the fan while not blocking airflow.
What I did was to wrap the fan and fan motor housing in "Gutter Guard" plastic mesh which I got at my local Home Depot, and fasten it with wire ties. It is flexible enough to wrap around the fan housing, and the openings are large enough that I cannot see the openings getting clogged. I did watch the temperature gauges after installing it and noted no change. It has now been wrapped in Gutter Guard for about 45 days and so far, no vibration meaning no leaves, at least for now.
In taking off the rear under shield, I had trouble removing two of the screws. Even though I thought I had every screw-head adapter made, when I tried removing two of the screws, the insides rounded out and I ended up having to drill out the screw heads. Therefore, I recommend that a dozen new stainless steel button head cap screws be purchased (also available at Home Depot) at the same time as the Gutter Guard is obtained. You likely will not regret having new stainless steel screws to put in, especially if the existing screws are rusted or have been removed and installed more than several times with an air impact wrench.
Here are the screws to get:
For what it is worth, here is the "Gutter Guard I used to wrap the fan cage and fan motor:
Also, while I was in there wrapping the fan cage and motor in Gutter Guard, I noted the make and model number of the fan in the event I ever need to obtain a replacement. It is a 12 volt SPAL Type 014-AP74/LL-22 which appears to be this fan:
Centrifugal Blower Detail | SPAL