Why is my heat not working properly? I have replaced the thermostat and flushed the heater core. The fan is working well.
Heat problem: The heater core is heating properly. It gets properly hot. Water is circulating through the hoses and feels warm to the touch. When I warm up the car, the heat works fine UNTIL I start moving. The heat decreases to "luke cool" within a few minutes. If I turn the heat off at the dial for about 10 minutes and then turn it back on again, I once again get very warm heat but only for several minutes. If I turn the heat dial on/off/on/off repeatedly when it is running cool, there is no increase in heat. Could I have a problem with the vacuum motor for the heater control door in the heater box??? If so, exactly where is the vacuum motor for the heater control door? My manual does not show or describe.this in detail. Thanks. Kate