i asked this when i first got my truck and its starting to cool off....
i changed the t'stat, made sure the heater control valve was opening, used the garden hose to flush the heater core and no crud came out and it dont leak or smell like anti freeze in the cab, and the coolant level is full

im not sure what it could be and running outta ideas, if i dont got heat by end of month im selling it pay of last of the loan and buying a different truck.....

any ideas please

 

Is the hose going into and out of the heater core at the same temp with the heat on high?
Use an IR temp gun to check inlet and outlet temps.

 

I would check the temp on the hoses if they are the same (hot) then a door inside is not opening.I would just feel the hoses hot is hot. You can manually move the valve by unclipping the cable and pushing it over. If you are standing in front of the truck Left is closed and right is open. Move it right and feel the hoses. If they are hot then a door behind the glove box is not opening. Don't forget to reclip the cable when you are done.

 

I think its possible you have an air pocket trapped and it stops the flow through the heater core. I'm pretty sure that's what happen to me once, then after draining the radiator and refilling and burping real good the heater worked. I have been removing the coolant hose that goes to the throttle body as I refill the coolant to let air out and then jack up the front end as high as possible and fill some more (with the heater core valve open of course). That gets some more air out.

Actually now I have bypassed my throttle body and have a "T" with an extra one foot of hose that runs up and is the highest point in the cooling system. I plug the end with a dowel pin and a screw clamp when not burping.

 

thanx 4 your help everyone.....i figured it out...the wire coming from the cool-warm switch is broke, so i have to reach under dash and open the door infront of the heater core...man the heat felt good lol