Radiator fan constantly running, heat not hot…?

I have a 1991 Mercury Capri (non-turbo), and the radiator fan is constantly running, and the heat is not hot. It's not overheating, and I just replaced the thermostat today. This was happening months before I replaced the thermostat. After I replaced it, the heat gauge was not as hot as it was, but the fan... show more I have a 1991 Mercury Capri (non-turbo), and the radiator fan is constantly running, and the heat is not hot. It's not overheating, and I just replaced the thermostat today.

This was happening months before I replaced the thermostat. After I replaced it, the heat gauge was not as hot as it was, but the fan is still running and the heat is blowing slightly warm air.

What could be the problem?
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