I have a 1996 f150 2wd regular cab with 5.0 engine. The heater isnt blowing hot air. I replaced the heater core and that didnt change anything. any suggestions?

 

Some of the reasons for the heater blowing cold/ cool air are;
1. Thermostat stuck open
2. Airlock in the heater core itself
3. There is a temperature blend door that when operating properly directs all incoming air over the heater core then into the vehicle. It may be stuck in the cold position and passing the cold air directly into the passenger compartment.
Were you able to determine that both heater hoses got hot when the engine warmed up?
If not the thermostat is possibly stuck in the open position or the heater core is air bound and will not allow coolant to circulate through it.
If both of those are OK , then check out the blend door behind the dash and see if it moves when you select various heat positions. (there could be an electronic issue involved in it's control).
Let us know what you find so far. Thanks

 

There may be an issue with the vent doors stuck open.

 

where is this blend door? do i have to take the dash apart to get to it?

 

You may need to remove the glove box to get in there.

 

im sure im gonna sound like an idiot here but is the vent door im looking for the same as the plenum chamber?

 

Before getting involved in the ductwork, is it reasonably safe to conclude that you did the simple things like check the hose temps first?

 

yes both hoses get hot

 

It would help if we knew whether your vehicle had a manual or electronic automatic temperature control.
In either case there should be a vacuum motor that controls the air inlet door. usually it is located under the right side dash assy where you replaced the heater core. Check that to determine if it is working and directing inlet air to go over the heater core.