OK, so after I acid washed the old heater core quite thoroughly and initially had decent heat, it stopped soon enough, so I bit the bullet and put in a new heater core using the tube cutting method. I was able to replace the worst corroded tube ( I think it was the intake) by removing the plate from the firewall and pulling it out and then wiggling the new (cut) section back up through the inside mounting bracket. CAUTION on trying that as the bracket has a round section that it has to feed through in order to get it back up through the firewall from the inside, and I was able to do it, but it wasn't that easy. Another thing I did was connect the new core with the lines cut as close as possible to the core (without cutting across any bends) to keep the rubber heater hoses as far away from the guide bracket for the lines as possible hoping to be able to replace the lines cover (held on over the lines by 2 screws), but in the end what I did was cut the lower half (or so) of the cover off since the rubber heater hoses increase the line diameter too much for the lower screw to be used, and was able to then screw the upper half into place to secure the lines in place in their original grooves. I would recommend to lube the outside of the lines with something before placing the rubber heater hose connections so you can use a longer piece of hose since in order to put the hose on, you need to slide it up the line first and then down over the bottom half. I had to do it twice because the first time the section of rubber hose I used was too short to get a good safe amount onto both sections of the lines. Finally, I did an "autopsy" on the old core and indeed, it was jammed with black corrosion. The outside was nice shiny aluminum, but the inside flow channels must be made of something else that certainly corrodes. The new core is working fine now several months later. By the way, though you can probably attach the intake and output hoses either way, I think that it does work best if you hook it up the original factory configuration. My takeaway from all of this is this: If you have a no heat or low heat problem and you go under the dash and can see the blend door actuator moving (you can see the rod rotating) then replace the heater core.

 

Thank you Dennis. is this actuator going to give me heat and cold when asked by auto or manual contol *****?
Just trying to verify and eliminate the other three actuators. need to get correct purchase.
Thank you.

 

sorry, the repsonce was for DONAHUES 17