How to Troubleshoot the Heating System on a Honda Civicby Chris Moore
If the heating system in your Honda Civic is not producing hot air, there can be a number of reasons for this. The biggest cause is a faulty heater core. You need to make certain there isn't another reason, however, especially since replacing the core is a complex and time-consuming affair. Other causes can include a stuck thermostat or worn-out hoses. The good news is that troubleshooting a Civic's heating system for problems isn't as difficult as its more complex air conditioning counterpart.
Check the condition of the drive belt on the air conditioner compressor. Replace it if it is deteriorated or worn. Adjust the tension if needed.
Inspect the hoses on the system. Look for cracks, hard spots or deterioration, and check for oil bubbles or seepage around the fittings. Replace any hoses where you find leaks, wear or other damage.
Look over the condenser and check for any debris inside like leaves or bugs. Clean the condenser with compressed air or a special "fin comb."
Look for damp carpet in the front passenger floorboard or steam/antifreeze vapor coming out of the vents. This means a leaking heater core; replace the core.
Check the thermostat's condition. It is likely stuck open if the engine takes a long time to heat up or stuck closed if the lower radiator hose isn't hot while the engine is. Replace the thermostat if it is stuck.
Feel both of the heater hoses near the firewall. If one of them is cold, this means either there is a blockage in a hose or the heater core or the heater control valve is shut. Disconnect the hoses and use a water hose to back-flush the core; if there is still no circulation, remove the hoses completely and flush them. If the core is still blocked, replace it.
- Running the heating system at least once a month for 10 minutes, especially in winter, will preserve the system by preventing the hoses from getting dried or cracked.