if it doesn't have a heater control valve then what could be wrong with it ?? on 1998 Ford F-150

If there is no heater valve, what could possible be going on ?

Asked by for the 1998 Ford F-150
You could have a temperature blend door actuator issue in the dash, failing to turn the blend door to "hot". You could have a flow issue at your heater core - it could be clogged? You could have a thermostat issue at the engine.
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What are the symptoms??

no heat in the dash