Might be a good time to pull it, clean it and flush it out good before winter. There are several different heaters for these trucks. If you can find someone who can order from Graingers you might be able to find a motor that will work. We have a good motor rebuilding shop here that might be a good option if you can find someone locally. I imagine that it will have to come out to remove the motor. Someone will be along that has dealt with the problem soon. That is the beauty of this sight.

Neil
http://community.webshots.com/user/neilhatten