after checking coolant level,thermostat operation and if heater hoses feel hot(be careful not to burn your hand) the temperature blend door is probably at fault. It directs the air from the fan blower motor either across your heater core or A/C evaporator, giving you either hot or cold air. Most cases the dash has to come out to replace this $80 electronic motor. Good luck, Mr.P
Replace heater blower resistor.located on the passenger side fire wall.I had same problem.New ,$200. wholesale (dealer only)I bought mine off an auto savage for $20. !!!Fan now works fine !!good luch !!