Heat Problem... blend door or heater core or???

[HIKELONG]

I have a 1998 Ranger clone (Mazda B2500) 2.5L 4 cylinder. The truck currently has no heat.

Here is what I have done so far...........

Drained and flushed the radiator.
Drained and back flushed entire system with Prestone back wash hook up kit. I did not use chemicals though.
I broke the heater control valve during the removal for back flush and replaced it with one from advanced.
I had a little heat as long as the blower was not turned up.
Not satisfied I did.............
I replaced the thermostat with a new Stant rated @192 degrees.
Now I have zero heat at all.
I think that this leaves only the blend door, the heater core, and possibly some code I read about related to the actuator.

I am reluctant to think its the HC since the radiator looks so clean when you look into it.

Would the blend door cause air to constantly blow out of the floor even when the blower it at the smallest dot and the other direction knob is at off?

Please advise how to proceed.

P.S. The fuses are all okay.

 

[Jack Flash]

sounds like a vacuum problem. the blend door operates by vacuum when you turn the knob. loose or rotten hose or the actual control assembly might be bad. I have bought the assembly for some vehicles from AutoZone. don't remember if it was Ford/Mazda p/u or not.