No heat from heater?

More then likely you have an air pocket in the heater core so we need to pressure test the system first just to make sure there are no leaks.

Here is a guide that will help with that:

https://www.2carpros.com/articles/radiator-pressure-test

Then we need to make sure the cooling system is filled with no air pockets and I attached a video on how to do that on a Dodge van which will be similar.

https://www.youtube.com/watch?v=s4OONuIzYVQ

Lastly here is a more general guide on how to do this:

https://www.2carpros.com/articles/coolant-flush-and-refill-all-cars

Once we know the cooling system is filled properly then we need to retest the heat. Let us know and we can go from there. Thanks

Check the heater core hoses when engine is hot, if one is hot and one is cool, then heater core is blocked.

If both are hot, then blend/divert door in dash.

HI:

Yes, the heater core could be plugged. However, that wouldn't cause the truck to overheat. I would have the radiator checked. It sounds like it may need boiled / rodded out due to corrosion. If the rad isn't allowing coolant to circulate, hot coolant may not be getting to the heatercore. Also, check to make sure that the radiator hoses are not collapsing when the vehicle gets hot (especially the lower rad hose). I've seen situations where the hose actually collapsed because it was old and weak. As a result, the vehicle overheated.

Check out this guide

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

Let me know if this helps. If not, we'll move on.

Joe

Does it get hotter (heat out of the vent) when you raise the RPM to about 3000-3500?

Typically it would just mean that you have an air pocket that needs to be bled out.

Could be either, first to check is the coolant level and life of the coolant. If its good then remove and test the thermostat to ensure it is opening / closing properly. If thats good as well than the heater core would be suspect.

The heater control valve is located on the heater core hoses.

First I want you to feel the hoses when the car is hot if one is hot, neither, or both are hot or if one is significantly hotter then the other.

Its very common for the heater core to be plugged
what always worked for me : Engine cool lower the coolant level Locate the two hoses running to the heater core disconnect them at the engine side leaving hoses connected to heater core throw the firewall use garden water hose and compressed air if possible run the water and follow by air throw one side and out the other and vice versa do that two to three times watching what leaving the heater core you are looking for the go flow and clear water to run through

Check the heater core if its clogged-up and if it has a heater control valve check that too-could also be a bad new Stat

First feel the heater core lines directly at the firewall, if they are both hot but no hot air coming out chances are you have a bad blend door under dash.

If one is hot and the other is cold you probably have a restricted heater core and you should change it or flush it.

If neither are hot it could be a bad thermostat or heater control valve.