In 1999, the FORD TRUCK heated doesn't work - 1999 Ford F150 Regular Cab

Start with the basics, check to make sure you have thermostat, h And the heater hoses. On a lot of the older cars. This would help prevent the older car from over heating. Just a suggestion.

it doesn't blow, or doesn't blow heat?

If you are talking about the belt for the ac compressor, yes the heater should still work.
If the blower is not working, you will need to have the blower motor checked for voltage and ground.

May need.heater core flushed out.

Either the water pump not working,,or you have a clogg some where..I have seen the impellor break on the water pump..The outside pulley was turning but the inside wasnt..

This car doesn't use a heater control valve.

fill your radiator, if that doesn't fix it then your heater core is most likely dead.

No this wont cause an overheat problem. Check the coolant level , check to see if the fans come on after it heats up. when the car is warming up you can check the thermostat, by touching the top radiator hose, after a few minutes the hose should get hot, this indicates that the thermostat opened up and is working. If it doesn't replace the thermostat. If it doesn't over heat until you start driving , then suspect the water pump. The impellers can slip on the shaft and not have enough flow to keep it cool.

you have the polarity reversed on thosse two items just swap the 2 wires i bet that will cure the problem.

the blend doors inside the system are what makes the heat ac work there are vacuume motors going to each door if the vacuume lines are cracked or broke the doors wont work and they can sometimes stick