On a 2015 model, unless you have cleaned it of dust, the fan is probably pretty well coated in dust. Pretty easy to do.
Unhook from the 110v AC power and take the negative terminal off the battery (batteries if more than one). You want no power of any type to the converter or breaker bus before you do this.
Unscrew the front and it should slide forward giving you access. If it is one of the very common WFCO models, you just take some screws out and the front panel will come off. Then the converter is screwed to a plastic tray that is held in with a couple of screws at the front bottom edge. Once you take them out, the converter will slide forward and you can clean the fan and fins, etc... Just vacuum them with the brush adapter on your vacuum. You should not need to unhook any wires to do this, but if you have a different model that may change.
Here is a photo of mine with the front panel off. See the 2 screws holding in the plastic piece the converter is screwed down to (converter is the silver thing with the fan on the right side at the bottom of the photo). This is a WFCO 55 amp model.
If your fan is bad or the converter fails, Progressive Industries makes a drop in replacement that is much higher quality. Runs a little over $200 for the part if you do the work yourself (a ton of youtube videos on what's involved are out there).