Hi , thank you for trusting us with your problem. The first thing you want to do is find out if hot coolant is circulating through the heater core. Start the truck and let it warm up to normal temperature. Now, gently touch both heater hoses one at a time. Be careful as they may be very hot. Both hoses should be hot (about 180 deg.) and should be close to the same temperature. If they are then we have a problem inside the A/C heater case. Next, we need to check the operation of the blend door cable. The blend door controls how much heated air is allowed to get to the vents. Remove the glove box and look for the cable shown in the following diagram: Now, watch the cable while turning the temp control knob from full hot to full cold. You should see the blend air door crank moving back and forth. It should move about 45 deg. of travel. If it does not then remove the cable from the crank and manually move it from one extreme to the other. It should move smoothly. Now, with the truck running and warmed up move the crank to one extreme and test for heat out of the vents. If you have no heat then move the crank to the other extreme and test again. You should have heat coming out of the vents with the crank at one extreme or the other. If you do not then you have a problem inside the A/C heater case. If manually moving the blend door crank produces heat then we have a problem with the blend door cable or the dash control panel. Grab onto the loose end of the cable and push it in and out of the cable housing and see if it appears to be broken. The cable should not move independently of the control knob. If it does then you have a broken cable or control assembly. Replace whichever is defective. Please let me know if you need any more help!