I have a stock '98 civic lx that has no heat to the passenger compartment. Initially, the temperature controller was not moving correctly on the dash and there was no heat coming out, although the blower and all controls for distribution were working correctly. I followed the steps as in the Haynes manual, and the heater control slides correctly, the valve under the hood opens and closes fine, but still no heat. I can hear the door in the heater control unit slam when I move the temperature controller back and forth rapidly. I changed the thermostat, flushed the entire cooling system including the heat exchanger. I sent water through the outlet heater pipe, moved the dash temperature control, and water flowed and stopped appropriately. There was good flow through the heat exchanger. With the car warm, the inlet and outlet heater hoses are both hot. The car does not overheat in city or highway driving, engine reaches proper temmperature and stays there, both radiator hoses get hot when the car is warmed up. No leaks anywhere in system. Car has always been maintained in top condition. Car has 120,000 miles, radiator was replaced at 50,000 miles due to a stone hitting the radiator. Timing belt and water pump were replaced at 75,000 miles. I'm stuck, help please.

NEW! Found problem. I believe there is a problem with the door not really opening any distance because of a problem with the mechanisms under the dash, or the door itself is broken, etc. Can parts be ordered to repair the heater control unit?

 

When you turn on your climate control, does air come out of the vents? Can you make cold air blow out or does no air move at all?

 

Chances are your coolent is low.......it wont reach the heater core thingy. So try adding some more coolant to the resiv.

 

Cold air blows out just fine, and diverts to all areas appropriately. Coolant level is fine in radiator and overflow.

 

Cold air blows out just fine, and diverts to all areas appropriately. Coolant level is fine in radiator and overflow.

 

Maybe there is a problem with your radiator fan that causes it to always turn on which would overcool your car. But i would think that the thermostat would compensate for that.

 

Radiator fan comes on and off, off most of the time since it is cold outside.

 

NEW! Found problem. I believe there is a problem with the door not really opening any distance because of a problem with the mechanisms under the dash, or the door itself is broken, etc. Can parts be ordered to repair the heater control unit?