No heater?

Just like raz said, the blend door motor has failed

Roy

Actually, the heater is most likely fine. However, there is what is called a blend door that is actuated by engine vacuum. Its position (open or closed) determines if you get AC or Heat. Based on what you said, it sounds like it is stuck which is causing you to only get cold air. Check it. It is part of the HVAC system and located near the heater core box.

Let me know what you find.

Joe

It's possible something did die. You may have to remove the blower motor for inspection. It may also be fungus and mold growing on the evaporator core from the moisture.

It could be blocking the heat blend door.

Did you bleed the system of air when you replaced the thermostat? Did you use a new gasket and torque it properly making sure that it wasnt leaking around it?

Was thermostat properly replaced and put in the proper way? Was proper thermostat put in?

Id still like it to be the thermostat since its a cheap part and very easy to replace.

There is a blend door control motor that is a common failure. Have a shop check it for you to verify and give you a bid.

Roy

Try bleeding the system you may just have air trapped?

COOLING SYSTEM BLEEDING
WARNING:When engine is operating, Do not remove radiator cap under any conditions. Failure to follow instruction may damage cooling system or engine, or cause personal injury. Always wrap protective material around radiator cap to avoid injury from hot coolant.

Except Villager
Turn heater controls to maximum and set air discharge to instrument panel vents. Turn blower to high. Fill cooling system with 50/50 mixture of coolant and water. Pause several minutes for circulation. Start engine and allow to idle. While engine is idling, feel for hot air at instrument panel vents. If air discharge remains cool and coolant temperature gauge does not move, coolant level is low.
Stop engine and allow it to cool. Top off coolant as necessary. Start engine and allow it to idle until normal operating temperature is reached. Hot air should discharge from instrument panel vents. Coolant temperature gauge should maintain a stable reading in middle of range. Upper radiator hose should feel hot to touch. Stop engine and allow it to cool. Top off coolant as necessary. Check for coolant leaks.

Is the engine running at a normal operating temp? If so, start the engine, let it warm up, with the heater on high, feel both heater core hoses. Both should be hot. Let me know what you find with that. Also, I will assume the blower motor is working. If that is where the problem is, when it doesn't work, you need to check if the motor is getting power.

Let me know what you find.
Joe

Yes the system is vacuum operated for direction etc. Check for a line off on engine near where work was done. Check at engine or vacuum reservoir under hood. Connection is at right rear of engine compartment on cowl, could be broken or disconnected etc.