Learning Furnace Repair

[Michael Herr]

I've been hiring out more lately, but I like to know how to do things even when I hire. 

My 90%eff. furnace at my personal residence has gone out. I'd like to buy a book or troubleshooting reference. 

With the older 80%eff furnaces I could easily diagnose most issues. 

Looking for a troubleshooting guide/process. 

Does anybody know of a good book or resource for learning troubleshooting especially for newer furnaces?