Troubleshooting 1995 HVAC controls

[Enginebuilder]

Truck is a 1995 ECSB k2500 w/5.7, auto transmission and A/C.

Problem: Heat zone selector does not work

Changing the selector from floor to blend to defrost does nothing; heat just blows more or less equally from all orifices no matter what setting the selector is on.

Is there a troubleshooting guide for solving this type of problem?

If you've run into this problem before, what parts did you change to fix the problem, and how can I test those parts?

 

[454ss]

my 97 has the same problem and I found the linkage that controls the vent doors or whatever from the little motor was broken/missing, probably got kicked with big hunting boots id guess as on mine anyway its the linkage closest to the gas pedal. look on that side of heater/vent box in the center of the truck and you should see what I mean. should see two small linkage arms with springs on them that are each hooked to a motor on one end and a door/flap or whatever on the other. ive got a thread in interiors started on it and am getting help there as far as parts I couldn't find locally.

 

[Enginebuilder]

Just checked, and the linkage appears to be in good condition. Will post a picture of the setup as soon as it gets a little brighter out. (6:30am here in Alaska)

 

[454ss]

possibly stuck/bound up door, I had a beer get spilled down the defrost once and it gummed it up when it dried and I had to dump hot water down it to get it unstuck. maybe try have somebody move the switch and see if you can feel or hear the motor trying to work, also check for power at the motor to make sure the switch is working.

 

[Enginebuilder]

Just checked the mechanism, and turning the switch causes the motor to actuate, and the lever moves. Still not getting a change in airflow direction. I'm thinking that the blend door is blocked or broken. Any advice on how to tear into it?

 

[454ss]

I haven't had it apart yet, when I get my parts it will be all new to me too.