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.

 

[my98nnj]

Did you get flow through the heater core when you flushed it? You had the valve off, did you try to push any water through that alone? Are both hoses, in and out from the heater core hot?

 

[joe doe]

I have a 1998 Ranger clone (Mazda B2500) 2.5L
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?

the blend door does nothing more than change the air from hot to cold and in between .
if your only getting air out the floor vents no matter the position of the setting then thats a different problem .usually related to vacuum

 

[HIKELONG]

Joe doe

I get air through all of the positions when I select the positions. They all work.

My concern/question is why is there air blowing out of the floor when the position selector is off and blower to lowest setting.(both knobs straight up)

These are the knob controls so the blower motor has no off but if the position selector is off (straight up) then I do not think there should be air blowing.

I think it could be both a vacuum problem and a core.

I read about clearing a code for a vacuum problem somewhere in here, but it was for a button or digital style control panel.

Any suggestions how to test this vacuum stuff?

Thanks for the assistance.

 

[HIKELONG]

my98nnj

Did you get flow through the heater core when you flushed it? You had the valve off, did you try to push any water through that alone? Are both hoses, in and out from the heater core hot? ........................................................................

Pretty sure that I did get flow through the core during the back flush kit process.
I probably should take a hose and blast directly into the heater core hose and see if it comes out.

I did not run water through the valve because it was a brand new part from advanced auto.

I do not not whether i should be checking the hoses between the core and the valve or the valve and the radiator?

Thanks

 

[HIKELONG]

Well thank you GOD!!!

Feeling HOT HOT HOT....................

I found and fixed the problem.

There is a vacuum line that runs from the heater control valve to somewhere under the blower motor. On my truck this vacuum line was a hard grey plastic line not a black rubber hose.

Anyhow the stock hose is way long. Longer than necessary in my opinion. After 300,000 miles this line wore down from rubbing on something or got burned against something. To me the line/hose looked burnt. This was about in the middle third of the hose. Spliced a new section about 2 inches long and problem solved.

I think that without this vacuum line connected / working properly the heater valve will not properly work. As in directing coolant to the heater core.

I hope this helps others.