[Lee H]

My truck with VA takes a while to get any decent heat blowing out the vents, several miles at least. Which controller do you have? I have the controller that uses the stock heater/AC controller. It's kinda lame, in my opinion, and does not function properly. Is the lower core tube hose connected to the intake manifold and the upper to the radiator or water pump? Next I would bypass the funky valve in the heater hose and see if that helps. If the hoses are correct and the bypassed valve does not improve things I would disconnect the heater hoses and gently run garden hose water through the core to see if it flows well.