How to replace heater core 1999 ford f150?
For diagnostic information on how to check the operation of the blend door and a cheap easy fix, check the heatertreater listing on Ebay or the web site at heatertreater.net. The dealer fix for the blend door is basically the same procedure for replacing the heater core, so it will be expensive. The HeaterTreater alternative will solve the problem at a fraction of the cost and work and is well within the capability of the average shade tree mechanic.