I oiled the fan, which seems to help. I'll order the fan that larryect described.
For anyone else trying this, you need to open the back cover, but then the fan will slide out without opening the electronics box. You don't want to open the electronics box. To open it, you have to release the strain relief on the battery cables, which is a pain to release and even more of a pain to put on again. Also, there is a wiring harness between the display circuit board and the main one. It comes unplugged when you open the box. Plugging it back in is a problem. You can't do it with the box open, because the wire isn't long enough. You can't do it with the box closed, because it is closed. The only way I found to do it was to slide the fan out and reach in through the tiny fan opening to plug in the cable.