Are the heater hoses hot or warm ?

 

You still have an air pocket in the heater core, or, it's blocked. Try back flushing the core.

 

I have back flushed the heater core last week and it is clear. I will drain the system tomorrow, re flush the heater core and fill it after I refill the system. Too cold here today to start this project, it's currently 12 with a wind chill of -5.

The truck is a spare vehicle, so it's not imperative that I have it done today.

Thank you all again for your assistance!

 

Well of course the heater stops working in winter.