1998 Sebring Convertible heater is blowing cold air even after replacing the thermostat. Any suggestions on fixing the heat?

Is your air locked slacken off top hose and make sure your getting a good flow of water no air

First you have to identify what causes the problem.
To do this you have to:
1) When engine is cold check the level of coolant. If it is low fill it up.
2) Start engine and check if engine reaches regular temperature. If your engine is not heated enough it means your thermostat does not work properly and should be replaced.
3) If engine temperature is normal, then check the temperature of pipes that go to/from heater core. These pipes are located up the fire wall (easier access is from the passenger side). If pipe/pipes are cold (even engine is worm) it means you heater core is plugged and should be flushed. Keep in mind, flushing the whole cooling system is different from flushing heater core.
4) If pipe/pipes are hot/warm, turn off the fan, switch controller to the hot position, wait for 3-4 minutes and turn on the fan. Note if the cold air blows first or warm air blows first but it cools down in 5-10 seconds. If the air blows cold than it is most probably the problem with blend door or blend door actuator.
5) If air blows warm first and then cools down, then while running engine and remaining the transmission in PARKING position, press on the gas pedal until your engine reaches 3,000 RPM. Check if your heater blows warm/hot air. If it does, then your water pump does not work properly and should be replaced. If the air still cold, I would suggest to flush the heater core.

It is most probably the problem with blend door or blend door actuator. But just in case I would suggest to follow the entire procedure:

First you have to identify what causes the problem.
To do this you have to:
1) When engine is cold check the level of coolant. If it is low fill it up.
2) Start engine and check if engine reaches regular temperature. If your engine is not heated enough it means your thermostat does not work properly and should be replaced
3) If engine temperature is normal, then check the temperature of pipes that go to/from heater core. These pipes are located up the fire wall (easier access is from the passenger side). If pipe/pipes are cold (even engine is warm) it means you heater core is plugged and should be flushed. Keep in mind, flushing the whole cooling system is different from flushing heater core.
4) If pipe/pipes are hot/warm, turn off the fan, switch controller to the hot position, wait for 3-4 minutes and turn on the fan. Note if the cold air blows first or warm air blows first but it cools down in 5-10 seconds. If the air blows cold than it is most probably the problem with blend door or blend door actuator.
5) If air blows warm first and then cools down, then while running engine and remaining the transmission in PARKING position, press on the gas pedal until your engine reaches 3,000 RPM. Check if your heater blows warm/hot air. If it does, then your water pump does not work properly and should be replaced. If the air still cold, I would suggest flushing the heater core.

I would have the heater core checked. It could be something as simple as a fuse but unlikely. not likely to be the thermostat as that would make the car overheat if it wasnt working.

sound like thermostat stuck open . flush coolant system . heater core could be stopped up.

I think you might want to start with thermostat replacement and pressure flush the system and as other suggestion check levels when car is COLD!!!!!!

bad thermostat

replace the thermostat it seems to be stuck

The hoses from your heater core should be very hot to the touch. Check the hoses going to the core from the water pump. It should be very hot. The return hose should also be very hot. Now check the hoses going to the core. If they are not the same temp, then your heater control valve is not working correctly or the vacuum is not working. At any rate, locate the vacuum line going to the heater valve. Remove the silver bar on the valve from the plastic plunger arm. You will have heat all the time now if it was only a vacuum problem. You can fix it later when it's warmer out. BTW a 200* thermostat will make your heater even hotter.

i have a ford fiesta 51 plate,when i turn on heater i only have cold air the thermostat has been fixed and coolant levels are ok heatin hoses are all hot,but inside the car its still blowing cold