Heater not working

Make sure the blend door is not broken and still blocking heater. You may be turning shaft but door might be broken from shaft. If that is the case then the hvac unit has tocome out to repair it.

With the engine at full operating temp and the problem is present, locate the 2 heater hoses where they go into the firewall and feel them to see if they are both hot to the touch. If they are.

The temperature is controlled by the use of an air mix door that is operated by an electric motor/actuator. This door can be jammed or the actuator can be inoperative or have stripped plastic gears internally.

These trucks unfortunately have horrible cooling systems. I usually find that I have to use compressed air to blow out the heater core. I put a rag at one end then blow through the other, you will be surprised at all the crud that comes out.

Are the heater hoses hot when up to temperature? Are there any coolant leaks? Heater core could be restricted or there could be a problem with a blend door not operating correctly.

Hi
Most likely a vacuum leak at control head. Pull out controler check vacuum source on purple line. If good maybe select switch the thing with all the hoses attached. If all good then faulty actuator that controls doors to change modes.
Hope this helps
Thanks for donate

I am giving you a walk through diagnostic on your situation. Just use the link below to get to it;

https://www.2carpros.com/articles/car-heater-not-working

Make sure the coolant is full. With the engine running, hot, and the heater on high, make sure both heater core hoses are hot. If they are, the problem deals with the blend door in the vehicle. If one is cold and one hot, there is no flow through the heater core. Flush it to see if that helps. If you have a heater control valve (I don't think you do), it will be an in-line valve on the supply line (heater hose).

First place to start troubleshooting for this would be to check your coolant level. If that is full, you may have a faulty thermostat. Test thermostat to ensure it is opening at proper temperature range. If this is good as well, you may have faulty or clogged heater core. You can feel the two hoses that connect to heater core ( going into firewall) to ensure they are both hot after engine has warmed up. If one or both are cold, suspect faulty or clogged heater core.

Well about the first thing is to check the core for flow. The easy way to do that is to disconnect the hoses under the hood. Then connect a water hose to one side and a drain hose to the other. Then try running water through the core. If you get a flow equal to what is going in then the core isn't clogged. If you get less or no flow the core is clogged.

Replacing the core isn't really hard BUT it does take some time. You have to pull the dash panel to get to it.

Power locks are
Fuse 7 under the hood if you also lost the power mirrors check this one.
Fuse 14 in the instrument panel block is just for the locks.

Try warming the truck, then carefully feel the heater hoses, are they both hot? If one is cooler than the other, you either have more flushing to do, or a replacement job on the heater core. Also if the system has a heat control valve on the heater hose, make sure it is working!