The variable resistor has probably gone bad
How do I locate the heater blend door actuator in a Ford f150 pickup
heater core hoses not hot
what is the year model? 1995
Try flushing the coolant system out
Take it 2 a mechanic. :D
It's the block heater. I had the same problem.
There are several common heater problems for a 1997 f150. A stopped up or leaking heater core, bad thermostat or clogged up blower fan housing all can cause heat problems.
Check out the Google Images and search for '93 Ford F150 heater hose'. you should find it there.
Inline in one heater hose underhood near the HVAC box (right hand side underhood.)
Sounds like a broken switch.
Dealer? Salvage Yard? e-bay? Craig's list? Hemmings?
You probably have a leaking heater core.