heater will not blow hot air only cooled

It's most likely the actuater located behind the glovebox. this is a common problem.If you want heat but don't have time or money to fix it empty your glovebox and theres a tab on the side of the glovebox that keeps it from opening all the way. push the tab in and open it all the way and straight back theres a lever. pull down on it with car warmed up and running and you should get heat immediately. If it works get a piece of a strong string or a big zip tie and connect it so it hangs down and you won't have to go thru your glovebox every time. nobody really notices it hanging down so it's not an eyesore, It's just a bit inconvenient.

Vehicle Application: 1998 Lincoln Mark VIII 4.6L Customer Concern: Vehicle came in for no temperature control from the heater. No heat. Tests/Procedures: 1. Pull codes from the Electronic Automatic temperature Control (EATC) system. With the engine running, push the OFF and Floor buttons for 1 second, let them go and within 2 seconds push the AUTO button. The screen should go blank with the exception of a small curser going around he screen. After 90 seconds a 3 digit code should be displayed. An 888 is a pass. A 024 or 025 are for Blend Door Actuator (BDA) faults. 2. Listen/feel the BDA for movement while changing the control settings. A low hum should be heard/felt. 3. The BDA can be removed for inspection. While the BDA is removed, grab the blend door shaft and feel the operation of the door. A loose or floppy door points to a broken door. Replace as needed. Potential Causes: Defective BDA Broken Blend Air Door Seized Blend Air Door