I bought the truck without heat as it needed a heater core. Now that I moved from Florida to Virginia mountain I needed heat. So I replaced the heater core. But now I turned on the heat but the air is cold the ac still coming on and no hot air. Any advice?

 

Vacuum leak? The switch controls vacuum tubes to different doors to control cold and hot. Mighty check the lever with the cable that controls the blend door.

 

I checked vacuum and replaced some still not working. The cable I took loose from the control and slid it both ways no change.

 

Broken blend door then, it's a common problem.

 

With the lack of use in Florida it is also likely that the deteriorating/ed seal has stuck the blend door in place.

For me, lots a cycling the door switch back and forth eventually broke it free.
I subsequently did a heater box rebuild.

 

Can you "feel" or hear the door thunk/move as you move the white arm on top of the HVAC box?

I'm also betting broken blend door. But you could just have a ton of air in the system. How are the heater hose temps into and out of core at the firewall?

 

I can here it thunk when I move the cable. I found the thermostat was removed cause I decided to check. I don't have one could that cause it to not heat up enough?

 

Yep, sure could. If the coolant isn't hot, your heat won't be either.

 

Absolutely! Pick up a good quality 195 degree thermostat, like a Stant Superstat and refill the cooling system, taking care to get all of the air out of the system. Budget thermostats tend to fail right out of the box or shortly thereafter.