Is your heater controls on "Automatic" or "Manual" Does it blow hotter with higher engine speeds and cooler with lower speeds? I'll need this information to narrow it down.
If it fluctuates with engine speed, this would indicate either a thermostat that is stuck in the open position (rare) or a partial blockage of the heater core.
If the fluctuation in temp has no correlation with engine speed, then this would indicate a failing control unit, sensor, stuck blend door inside the HVAC unit, or a leaking vacuum line/solenoid that controls the blend door.
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Sunday, November 21st, 2010 AT 6:55 PM