Freightliner columbia wont blow heat into cab have replaced thermostats and heater core blend doors work heater core gets hot and blower works but air from vents only gets to 80 deg

"Air flow is fine. Air movement from floor to dashboard to defrost works fine. but filed to say air flow hot works. just air." I can not guess this so will do it all.
it is just a liquid to air heat exchanger. (tech, pure)\
to get hot wire the hot core blend door must be fully open.
that is goal 1. we just watch the drive motor actuator to do that.

blower is good. .
heat comes from the engine
so we scan the PCM for PID ECT temps readings/
180f to 200f + any real scan tool can do this. easy.
150f is STAT stuck open or missing and BAD for sure. (bingo)"?

if lower the thermostat 20 year old is bad and for sure that old. yah
or using IR thermal gun a $15 tool the thermostat housing shows up near 180f+ good, 150 no.
then I check both cab heater core hoses,_ tubes.(at fire wall)
the are both hot,. 180f+ if yes good or one is way low that means the core is blocked.(even hand touched hand flies off test is GOOD.)
ok core is hot, we not go to CAB side.

hot air fails:hard. (i guess, ?)
that means the damper door is closed, on the heater core.
some cars have left and right dampers, (jeep commander does)


if a blend door jams ,as seen by eyeballs does not move or limited range we remove the motor there and turn the door hinge shaft by hand end to end to prove it does not jam. end to end.
ok door is free as a bird.
if ok the the motor actuator is bad (or weak) oem parts work better.
same goes for all doors, mode./blend/ or recirc/fresh failing
and some have left and right blend.
and sure VENTS, if some vents work not say so

AC is a whole other story ,,not doing both now me.

ASKING WHAT?, A WILD GUESS OR DOING TESTS WITH TOOLS?

IS THE HVAC, (HEATER..COOLER) CONTROLS THE AUTOMATIC OR MANUAL VERSION, NOT TOLD
NO CAB HEAT?
BLOWER DEAD ON HIGH OR ONLY DEAD (SILENT) NOT ON HIGH.?
ENGINE TEMP AT 180F TO 200F? (THERMOSTAT MISSING OR STUCK OPEN) I USE AN IR GUN TEMP METER.
THE HEATER CORE AS 2 TUBES. (HOSES) from engine coolant loop to the CAB core,(using same gun)
both tubes 180f up is good , if one is at very low temp that means it is clogged, (core packed up.) some cars have water valve here dead.
ok both tubes hot ,170f us good, I point my IR gun to metal pipe part for the best readings.
ok core is hot, heater core and the problem is CAP HEATER AIR DISTRIBUTION FAILURES.
2 CAUSES, CONTROLS BAD, OR THE DAMPER ACTUATORS ARE BAD. FOR SURE BLEND DOOR. STUCK LOSED RENDERING THE HEATER CORE USELESS.

A TECH USES THE OBD2 SCAN TOO, AND READS THE ETC PID LIVE DATA CAR HOT AND RUNNING,
2005 THERMOSTATS ARE MOSTLY NO GOOD.
I'D NOT TRUST MY ENGINES WITH ONE THAT OLD.17YO
THE LIVE ECT DATA MUST BE 180F UP, NOT BELOW EVER.
IF BELOW THE THERMOSTAT IS NO GOOD.,MISSING OR ONE OF THOSE FUNKY, FAIL SAFE THERMOSTATS INSTALLED AND IS BAD.

I USE THIS. AND SCAN TOOL BOTH. TO FIND CAUSE.

https://www.walmart.com/search?q=IR+GUN&sort=price_low

THE SERVICE MANUAL COVERS THE DAMPER TESTS.
WHAT i DO AND THE BOOK TELLS US.
IT HAS ME WATCH THE BLEND MOTOR WORK
the steps are , this in generic format.
gain access to all damper motor actuators
glove box pulled ,kick panels pulled.
now turn the knobs on the heater controls
try hot and cold and the blend door must move from end to end.
if not the motor is bad, or the controls are dead.
the mode motor (recirc/fresh) and vent motor selectors

if blower is heard on high but not lower speed, the resistor block is blown out. if climate controls is here, then the blower controller is bad or the blower motor is dead, we hot wires blowers in place to test them.
this this is the short version, of how.

the MACRO answer is.
engine coolant never gets hot, fix it.
heater core is not hot, (clogged fix it)
air distribution is failing so test dampers or fix dead blower.

USA car or NOT, ?????????? what engine?
with or with out electronics temp control options
I can't see the dash to go ahhhhhhhhhh
EATC for sure has named bend door.
fuse are first are they all good>?/
below 120f coolant the blower is taken off line.
well there are only 2 causes.
one under the hood, engine not hot,. thermostat bad.
two, cam dampers failing. or heater core clogged up. inside.

a tech does simple tests to see which end of car fails
even a finger,test. to the 2 tubes passing the fire wall to the heater core. (ouch,ouch) test tube,1 and 2, are 180f to 220f hot that is good test for engine bay good
and the core is not clogged
if hot /cold is fingered, that is clogged up core.

the first question that pops to mind also is does the cab core have hot water valve. most cars now do not.
i just look at the 2 heater core tubes for water valve and even cable drive or vacuum drive to it.
there is vacuum servo called heater door actuator
or has below EATC

here it is and if dead and stuck in blend cold ,heat ends


what I do is 2 things, (working cab side)
core tubs both hot 180f UP
i watch all damper doors, actions in all modes.
3 or more.
if say blend door is dead, i move it by hand,
some even wire (bailing)wire it to hot and drive all winter.
until spring and fix it then.

yes one has vacuum blend door
and yes other model has gear/motor actuator EATC blend door servo./

what you, nobody knows
but id pull off all lower panels to the dash and look first
sure whole if core is hot, 2 tubes, sure would

If your thermostat is staying open then it won't get hot in the cab,if the heater is bad,it will leak and fog up the window,another cause could be the blend door is stuck close,or the valve is stuck close and antifreeze can;t circulate thru the heater core.When you first start your car does the thermometer on dash go up then cone down,if it is then thermostat is good.

If air is blowing,just not hot, you either have a plugged heater core or the control valve is stuck (manual heater) / blend door not working (climate controlled).

CHECK THE BLEND DOORS ON INSIDE OF TRUCK UNDER THE DASH IFE THE BLEND DOOR IS STUCK IT WONT BLOW HOT AIR

Check for correct coolant mixture. Also you could have a thermostat that is stuck completely open causing it to flow straight threw the engine block, cylinder heads, heater core, an radiator without stopping long enough to heat the coolant up to provide cab heat. It could also be a clogged heater core. Or a blend door on the HVAC box that is not allowing the heater core door to open. Hope this helps.

If the heater hoses are getting hot, the problem may be a faulty blend door under the dash. The blend doors direct air thru the heater core and the vents.

first feel the heater core hoses see if both are hot if so then your problem is in the blend air door must be stuck on cold. is your blower motor blowing cold air if not your blower motor might be the problem. the blend air door is down by the blower motor.

you need to check the blend door in the heater box it maybe broken or stuck.the blend door switches between the heater core and ac evaporator to provide a mix of temperature