How Your Car Heater Works
1991-94 Mercury Capri Heater
Your car heater and defroster are fairly basic systems, most have not changed over 35 years. While the controls may have become electronic versus manual, the heating system consists of a blower case, a heater case and ducts in your dash. The heater in a 1991-94 Mercury Capri is directly center behind the dash. The blower, which pushes inside or outside air, is mounted to the dash behind the instrument panel on the passenger side. Like many cars, the air is controlled by a control panel manually with cables. Newer cars do it electronically.
The control settings will basically allow air to circulate in and around the heater, as it does, the air becomes hotter and enters the compartment, or, the air is circulated away from the heater so it does not get warm before entering the compartment. The temperature control will allow fresh air to mingle with the heated air or not at all for hot temps, depending on the lever setting.
Most car heaters last forever, if you are having heating issues, it may because of the air distribution and malfunctioning doors that either open or block air passageways. Most cars have five settings to direct the air. If your blower switch is in the OFF position, but you feel air blowing when not moving, it is an electrical issue of some sort because nothing should be blowing. If you have the blower on a setting that should have air blowing but does not, either your blower motor is gone or there is an electrical issue.