It has never had heat. The previous owner had the same problem. The radiator is full. The radiator hoses to the engine are warm. The engine thermostat has been replaced. The heater hoses have not been tampered with. I pulled a hose off what looks like a temperature sensor in the heater hose between the engine and the firewall and water came out; I could see through the sensor and it was not blocked. The fan works fine; it just blows cold air even with the temp lever all the way on hot.