Have a 92 Nissan sentra and the heater only blows cold air

SOURCE: heater blowing cold air

squeeze the hoses to get any air bubbles out and refill coolant as necesary. are you sure you put thermostat in the right way? may be backwards. also may be your sensor.

SOURCE: heater blows cold air have replaced the thermostat

sounds like the controller went bad use temp checker see what your temp is at inlet of heater core from hose

SOURCE: heater blows cold air, replaced thermostat &

try to back flush the heater core. and if that dont work check the blend door it see if it is working.

SOURCE: Heater doesnt work blows cold air, replaced

This is what I did to solve the exact same problem.I got a pump that you can hook to a drill that has garden hose connections on it.I made 2 hoses to pump into my heater core and hook to the pump. I bought some radiator cleaner at Auto Zone and put it in a 5 gallon pail with about 2 gallons of hot water.I pumped the cleaner from the pail into the OUTLET side of the heater core.(By going in the outlet side you are back flushing the core.) I put an old cloth over the top of the bucket and let the outcoming cleaner run onto this cloth acting as a filter for the dirt coming out of the heater core and let the pump run about 10 minutes. Believe me,A LOT!!!!!!!!!!! of dirt,rust etc. came out of my heater core. The heat now works excellent! Good luck.

SOURCE: 2003 Nissan sentra 2003 gxe, had 4 yrs, no

Start the car up when it is cold and rev the engine up for 30 seconds,loosen up the radiator cap and see if there is pressure there..If there is you probably have a bad head gasket...Caution do not open cap if engine is warm...