I have a 2007 Ranger with a 3.0V6,I'm having heater problems.
Maybe you need a new thermostat.
Whats the coolant look like? What's your temp needle staying at? If you still have original coolant do a "dump and flush" then locate the hoses going through the firewall to the heater and reverse flush ,,, sometimes the crud coming out of there will answer your problem.
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