I need wiring diagram for a trane air handler model no. Bwv724a100d2. It Has electric aux heaters and the diagram on the squirrel cage is faded out. It was installed in 1985.

Sorry, but you are most likely going to have to contact a train dealer. Train, much like Lennox, is very strict on who they sell parts and information to. Licensed dealers are your best bet when it comes to such brands. You may get lucky and find one on the web, but they do a pretty good job of keeping that info out of the general publics reach on the web. Good luck, and please do let me know if you find a link to it.