Why does my heater in my 1990 mercury topaz work when it is in park but as im driving it loses it heat
by 
BRADY12
ANSWERS: 2
-
Sounds like you may have a bad thermostat. When you are parked there is little airflow throught the radiator so the engine can warm up to provide heat to the heater core. Once you start driving the failed thermostat allows the coolent to flow through the radiator where it is quickly cooled by the airflow leaving no heat for the heater core. A thermostat is not difficult to do on your own or expensive to have done. Hope this helps.
-
Another possibility is that the self-adjusting clip on the temperature control cable is faulty. Perhaps when you first move the temperature lever, it holds the temp door open properly then over time it shuts and allows cold air to come in. Here's a repair procedure: http://www1.autozone.com/az/cds/en_us/0900823d/80/12/75/99/0900823d80127599/repairInfoPages.htm
RELATED QUESTIONS
Copyright 2023, Wired Ivy, LLC