I try to set up my heater and I have a 4 blink led light in the unit trane XL80. What does that mean?

I believe it indicates a limit switch has tripped. This is a safety switch to turn off the furnace if it gets too hot. Make sure the filter is clean so that air will flow easily.

Also, try to power off the furnace for a few seconds to see if the switch will reset itself. It may, or it might need a manual reset.

Check out this page (http://www.doityourself.com/forum/gas-oil-home-heating-furnaces/376006-newbie-question-open-limit-switch-trane-xv90.html) for some more ideas.

Good luck,
WallyH