Chosen Solution

heater is blowing cold air

Does it heat up after the engine is warm or is it cold no matter what? If it heats up eventually, then that would be your engine thermestate, replace that and you will be good go. If it does not heat up at all,

  1. check your coolant level
  2. Do you smell antifreeze in the cab of the truck? 2a) If you do that mean you have a coolant leak in your heater coil. It is the coil that connects to the engines cooling system that distributes heat to the internals of the cab.
  3. If fluid is good, when is the last time you flushed your coolant system?
  4. If you are flushing your coolant system, change out the heater coil and check and make sure all the valves are in working order
  5. I would buy the repair manual from a local autoparts store and follow their procedures, that way your not wasting time guessing :) Happy Fixxing.