Ford Repair: heater works sometimes, heater hoses, coolant level

Question
we bought a 2000 ford taurus se with a 3.0 liter engine with 125,000 miles on it. I bought a haynes manual to study the electrical layout of the heater control circut. the problem with the heater is that once in a while the heater will not put out hot air. the previos owner replaced the heater core which did not fix it. would this problem be in the temp control or the blend door motor? any advice on how to trouble shoot would be appreciated.

Answer
either or and maybe something else-first be sure core is not clogged or restricted-next time you don't have heat feel of both heater hoses at the core they both should be hot-if one is not core is clogged if both is not check thermostat and coolant level.

if both hoses hot you probably have a bad blend door motor but it would pay to have it checked out instead of guessing. good luck