Would it hurt the electronics if I removed the fan at the rear of the tender ?
I was considering this because my Bachmann K-27's don't have fans.
Would the electronics over heat without the fan?
It depends on how hot the environment is that you are running in and how hard you run the locomotive. I would personally try to find different shaped batteries and keep the fan.
Mudhen,
After re-working the tender on my K27 to retain the factory electronics, add an AirWire receiver and a Phoenix PB11 sound, batteries, plug and socket to separate the shell from the floor, relocate the speaker and factory electronics and install a 5600mHa battery pack, i ADDED a small CPU fan in one corner of the floor with a voltage circuit to reduce it to 12 volts. I also added a toggle switch and re-routed wiring with another voltage control circuit to allow the AirWire to run either from continuous track power or the battery. Some judicious planning will allow a lot of stuff in a small package.
I don't have a fan in mine, and have not had any issues at all in the hot Colorado summers. It's not uncommon for me to run mine 6 - 8 hours straight during an open house. (It's my most reliable loco.)
I've got the Revolution plugged into "the socket," and a Phoenix board taped to the side. I kept the coal load removable, and just drop a 2600 mAh 14.8v Li-Ion pack towards the rear of the tender. When it goes flat (3 - 4 hours running) I just remove the coal load and insert a fresh one. Just be careful not to bump the track/battery switch when you do, as you'll find you won't have power if you do that despite the battery being fresh. (Not that I've ever actually done that, mind you. That's a purely hypothetical situation. ;)
Later,
K