AC/Heat Issue

[97 T Hoe]

Hey All,
New to the forum. Never needed to join before now, but need some help.
97 4dr Tahoe, air will blow from all locations except floor. Any ideas?? Bad actuator, bad controls???
Where are the actuators located?
Also, where is the windshield wiper pulse board located??

 

[samotahoe]

there is a little door inside the dash that re-routs the air to whatever setting you want to change it to. that door either is stuck in a certain position with some debris causing it not to move or the motor for that door is bad. only way is to test the wires to see if it has continuity,and/or you can turn the dial on the dash and listen to see if you can hear the door move around

 

[lesterl]

down at drivers feet, look to the right should see the mode door actuator. Ignition on, adjust the mode and watch for the shaft to turn. If it doesnt turn when you adjust the knob then you need a digital meter, DC setting, looking for low DC volts. 1 wire on the actuator will be a ground, another will be a power feed (12v IIRC), the third will be the reference signal and will vary from 1v-5vdc and will reflect the position of the knob. No varying voltage would mean a bad control head, having the varying voltage and no movement of the actuator would be a bad actuator or jammed shaft. Hope it helps....

 

[97 T Hoe]

Thanks for the info, but apparently that is not the problem. The actuator seems to be working properly.
So here is what is going on. The air blows a little at the floor and more at the defrost, this does not change regardless of the position of the selector. It does blow out the mid level vents only when they it is selected, but still at the floor/defrost.
Is there another actuator that would be the culprit?

 

[lesterl]

AFAIK there are 3 actuators, the one at the drivers feet selects the airflow position, the one behind the LH side of the glovebox is the temperature selection actuator, there is another on top of the whole mess and it is a recirc/ fresh air actuator.....

 

[lesterl]

Perhaps the mode door is jammed? I would start with mode in center selection (ign on), turn ign off, unplug actuator, remove actuator, turn ign on (fan up), turn shaft by hand to see if jammed and airflow is good/ bad, before hooking up actuator make shure ign is off and reinstall with shaft in same position..... If manual changing works, I would try a new actuator (or swap out the blend door one at least)....

 

[97 T Hoe]

I already replaced the one at the floor and while it was off, i moved the door back and forth, didnt seem to affect the airflow. Could there be an issue inside?

 

[lesterl]

Could very well have internal issues with airbox......

 

[justimagination]

If it is blowing through the DEFROSTER(windshield) area, look for a "VACCUM LEAK". One simple test while driving, while it is blowing out the defroster duct, start up a hill and really get on the gas, if you loose the blowing off the defroster area, find your leak, probably under the hood area. The heater/ac system default blows there when there is not enough vaccum. Good luck........JMHO
david g./FONT]

 

[lesterl]

justimagination, the 97 series c/k trucks employ an electronic control system, no vacume actuators are involved, the system employs 3 electric servos controled by the box with the 3 knobs on it.