1992 cadillac seville heater air mix trouble, semi warm on drivers side and hotter on pass. side with defog. button on, can't make air come through front vents, no codes are showing, can you clear up problem with programmer.

DTC B1340 Air Mix Door #1 Movement Problem !
The heater and A/C programmer supplies voltage to an internal motor that drives the air mix door. The heater and A/C programmer monitors the air mix door position feedback from a sensor on the motor. If the air mix door is requested to move but the feedback voltage does not change, the heater and A/C programmer will store DTC B1340. If the air mix door feedback indicates that the feedback is near the hot or the cold extreme, the DTC will not set. Evaluate the operation of the air mix door through self diagnostics as described in the test description.
Test Description
Perform the Diagnostic System Check before continuing with the diagnosis of this DTC.
A Scan Tool allows for the direct control of the air mix door by observing the following conditions:
• The air mix door position feedback value
• The value`s difference from the air mix door commanded position value
These readings indicate a fault internal to the heater and A/C programmer in the air mix door sensor feedback.

Did you perform the Diagnostic System Check?
--
Go to Step 2
Go to Diagnostic System Check
2
With the engine running, connect a Scan Tool .
Turn the dual zone to OFF (passenger temperature offset at 0 or OFF).
Exercise the suspect actuator using the temperature control on the control assembly.
Is the door being commanded (COM) to the proper high and low values?
COM High 100 %
COM Low 0 %
Go to Step 3
Go to Step 4

If you are unfamilier with this , i suggest you take it to a ASE certified repair shop or the dealer .

Heater or mode door actuator bad , possibly ! You can look on youtube for videos showing how to change . It can be easy or very hard to replace . You could have it checked for DTC's diagnostic trouble codes stored in the heater control head . dealer only !

many cars automatically kick on the air compressor in defrost, to dehumidify the cabin air

you simply have an electrical relay problem or a stuck door in your vent not allowing the flow to be equal ..I have found all kinds of issues like a small toy or something that was somehow dropped into the vent area ..also once i opened some duct work and pulled out dead mice ..I know ewww ..good luck

theres one in the trunk on driver side might be there

I believe that your Seville has dual climate controls.So it sounds like a "Blend Door Actuator" problem. It's stuck and so it's not adjusting the mix of warm or cold air; that's how temperatures are controlled in your A/C heat system. Fault code(s) stored in the HVAC control module should be available to assist with diagnoses. AutoZone will perform a free diagnostic scan.

i've been down here too myself, and discovered that the temp control motor, located in the bottom of the glove box, which you can access by clearing all your stuff in in and opening a small door.
you can adjust it manually, and see if it changes, if yes, the switch can be defective, as well as the motor, the switch is the most likely problem.
but adjust it manually first.

Phil
grandmotors.ca

it's your computer modul it went out i had the same poblem know it works

look for loose vacume lines

The air doors are controlled by actuators that on of them or so may need replacing.