Concerned Truck Owner

If you know for fact that you have "hot water" flowing through the wet side of the heater core, then you must have something obstructing the air on the dry side of the core. It might just need a good vacuuming.

It could also be that the mixer door is not operating correctly. This could be either electrical, mechanical or vacuum actuated. I am not sure which your truck is so you can check on that yourself.

Yes, the door may flex a little bit when fully closed. This varies depending upon the door design and material, as well as the HVAC system design and how the control logic to open and close the door is set for the vehicle. It is not accurate to use the analogy of bending a coat hanger back and forth. (I imagine you are referring to a metal coat hanger - similarly a metal paper clip.) I am not familiar with this particular door, but automotive HVAC doors that I have seen are polypropylene or polyamide based materials. The fatigue life in bending of these materials is exceptional. The photos of failed doors also did not fail in the mode which you described. The photos were not good enough for me to tell how/why they failed, but it was not a door bending fatigue failure.

Also, the link you have shows to replace the plastic door with a metal one. You need to be very careful when making a change like this not to create a new failure in another location. If the system was designed with some intended flex before the motor stops driving the door, you risk breaking the teeth off of the stepper motor, break the door shaft, cracking the housing, etc. The original door lasted for 15 years in service. If indeed the door is broken, I would still recommend another door like it. I imagine that another 15 years of service will suffice for the vehicle. You can probably find one in a junk yard for a reasonable price.

HI, I had the same on my Range rover. It was the heater matrix partly blocked / furred up. The water still ran through the un blocked part of the matrix hence the air being luke warm as it mixed with the cold air which came through the blocked part. Try reverse flushing with a hose pipe . If this does not work then it will be a new matrix.

Good luck, Paul.

Yes, Place the dynamite as close to the heater rad as possible to avoid blowing the mascot off the hood.. if I can help somebody then my life will not have been in vain,vane,van aw just pick one.

Bazzer

You might check to see if some lightweight foreign object was sucked into the return plenum and lodged against the heater core or in the bypass door. Plastic shopping bags tend to do that - had one do that in my truck a few years back..

Lyn and Solar eagle are right, you should have bought a Chevy..

Ford rangers have a vacuum line that comes from the "globe" (located under hood on passenger side front) to the firewall, it is about 1/8" dia. black tube that is located too close to the manifold. it melts and seals inside. it may look "ok", but you need to test it out. all the functions of the heater and air conditioner depend on this little tube.

rmacusa is right...sometimes something like plastic shopping bags can find their way to the rad core. maybe check from the bottom of the wiper bay and see if leaves or pine needles may have blocked the airflow to the heater core.