My car overheats when the heat or ac is on My car is a 1992 Lincoln Towncar

SOURCE: 96 LINCOLN TOWNCAR STUCK ON HEAT ONLY !

The heater and a/c blend door actuator motor is located behind the center of the dash just below the windshield. The steering column must be detached and lowered and the dash must be removed to access the blend door motor.

SOURCE: Cannot control my AC blower on my 2001 Lincoln

sounds like your switch contacts are shorted closed.. try disconnecting the switch for inspection and use a volt ohm meter to inspect switch across contacts...

Testimonial: "At first the blower stop working. When I ran a separate ground directly to the fan motor it worked but then I found out I had no control. "

SOURCE: Lincoln LS 2000 V6 overheating after reparing intake manifold lea

Couple of items you need to check. Make sure that your radiator is flowing properly. Often after sitting dry, blockages harden up and flow less than before, overheat originally before repair can also free up debris inside engine and add to plugging of core. Make sure that fans are operating especially with ac on. If you did not change thermostat during repair, change it. Not often but they can sometimes partially open, restricting flow. Also make sure that coolant is at correct concentration (50/50) and that there is no air trapped in the system.

SOURCE: 2002 lincoln town cae blower problem

if you have checked the fuse and they are good and there is power going to the blower replace the blower you should be able to pick one up at a good salvage yard at half the cost.