No cabin heat

[dcarrb]

Condition: No heat from any air register, in any climate control mode. Airflow, blower, and AC operation appear normal. Air from heat and defrost registers is chilled except in ECON mode, which blows ambient air.

Diagnostic codes:
—13 sun load sensor (normal; car was parked in my garage)
—31 Air mix door (PBR) faulty
—33 Mix door faulty engine

Questions:
1) The actuator on the passenger side of the airbox (with a plastic bellcrank and linkage rod running parallel to the firewall toward the driver's side) does not move at any thermostat setting. Is this unit the code 33 "mix door engine"?

2) Would failure of this unit also explain why the AC compressor is engaged even with the thermostat set to 85 and the system is trying to provide heat?

Thanks in advance.
dcb

[Subaru Alliance]

I can't say for certain, but as an educated guess I would say both of the 30 faults are climate control related. Especially the air mix door faulty engine, because when working properly the car won't only give you max heat and max cold, the fact that you can get temps in the middle means that it will mix hot and cold air together to get you the temps you set it at.

sounds like the code 31, would be why you aren't getting heat at all, and sounds like the code 33, would be the motor that would continuously make adjustments by opening and closing to maintain the temperature in the car, as the temp in the car changes.

IN EXAMPLE If it's cold outside and you have it set on 75, the car warms up to 75, then adjusts to maintain, then say you open the window to smoke or whatever, the temp in the car drops, the mix door engine, would adjust to put out heat again. and bring the temp back up to 75.

not being a smarta$$ but this is all assuming you have the radiator filled to the proper level, and the heater core is not clogged. Another thing you could look for, is a schematic, the internal thermometer should give some sort of signal to the mix door motor, if that wire was broken or loose, that maybe part of the problem, but I would think at that point it would default at either max heat or max cold,(no temps in the middle) since there would be no signal to tell it which way to adjust.

I would say yes to question 1, that would be the mix door engine. and for question 2, the a/c compressor will run when putting out heat, if it is on DEFROST, purely for efficiency. Try it on AUTO with the temp at 85, but if you hit DEF then yes the A/C compressor will run regardless of temp setting. hope this helps, at least a little

[dcarrb]

Setting AUTO, thermostat @ 85, AC compressor and radiator cooling fans run and "conditioned" air comes out the floor registers. Not one calorie of heat from anywhere, regardless of setting. Failure was abrupt and complete.

Coolant level and temp normal, both inlet and outlet heater hoses hot, so it's not coolant/heater core related.

I observed proper operation of that "mix door engine" on my other car; the question is, is that unit shot, or is it inoperative for some other reason? The bit about the AC compressor running with the thermostat on 85 seems odd if the problem is noting but an air-mis door.

It occurred to me to swap 'em but I'm too old and fat and farsighted to relish fiddling with something up under the dashboard of my car until absolutely necessary. Thought I'd seek counsel here first. I appreciate the input.

dcb

[Subaru Alliance]

If the wires are easy to get to on the air mix door, maybe you can just unplug them, and see if you're getting power there, at least that will rule out wiring up to that point.

If the motor on the air mix door is easy to get to, take it out and tear it apart, I would be willing to bet it's something as simple as filing the brushes down or replacing them.

If it's not an easy fix, I am parting a 92 AWD, so if anything i'll just give you that one. I would rather parts go to a fellow SVX'er than just let them rot away in a junk yard.

I will look at the one in my parts car, just so i can "see" what you are talking about.