a/c help

[kev2809]

hey guys, round 2 trying to fix the a/c in wifes 02 tahoe. around october last year i thought i would get a good start in prep for this coming summer, cuz it gets hot as hell down here. well, i changed out the compressor, dryer, and orifice tube screen (had an a/c shop do everything). the compressor was rebuilt, dryer was new. he charged it up, and it actually blew cold when the truck started up. but when it gets to operating temperature (little before 210) the air blows warm. when i move the temp control to heater it doesnt change, stays the same warm air temp the entire time. i even switched controls from my 02 sierra and it still does it.

so, i googled a bit on the internet came across a blend door actuator. i found the one behind the console...took it and apart and plugged it back in and the motors were turning as they should it seems. found the driver side one next the gas pedal, pulled that one as i did the other one..and the gears worked as they should.


now, when i reached up under the dash on the passenger one and manually closed the valve, my ac stayed cold. when i turned it, the heater started working.

so, question is, would the motor be too weak to turn the valve? i havent tried re installing either one because im going to have to get the gears set in the right spot first...i accidently moved them.

[usmcchevy]

Any AC guys?

[clinebarger]

Do this test, If the voltage values are correct...Replace the air temperature motor....If not correct you have a wiring problem or the control head is bad.


1. There are 5 wires at the motor.

2. The Brown wire is ignition power.

3. The Black wire is a ground.

4. The Gray wire carries a 5-volt reference from the control head to the temperature motor.

5. The Light Blue wire is the feedback circuit to the control head and should measure between about 1 volt (cold) and 4 volts (hot).

6. The Dark Blue wire is the motor control circuit sent from the control head.

7. When the control head sends out 5 volts on this wire, the motor moves towards cold.

8. When the control head sends out 0 volts, the motor moves towards hot.

9. When the temperature motor reaches the correct position (as measured by the feedback voltage on the Light Blue wire), the control head sends out 2.5 volts. This voltage signals the temperature motor to STOP and hold its present position.

10. Check for correct operation of these voltages.

11. In some cases, the air temperature door does not fit correctly in the plenum and will cause the air temperature motor to travel too far. This will cause the control head to become confused and operate erratically.

TO RECALIBRATE: When replacing the air temperature motor, do not operate it without installing it first. The control head initially calibrates itself by driving the blend door to full cold and full hot. If the motor is operated before installation, the expected "end of travel" voltage will go beyond recorded limits. This will shut the control head down. To fix this problem, remove the cover from the air temperature motor, and using a 9v battery, drive the motor close to a center position. Then, install the motor and remove all key on and memory power from the control head for about one minute. When memory power is restored, start the engine, do not change any settings. The control head will automatically recalibrate itself for both cold and hot positions within one minute. Normal operation should occur after this is completed.

[kev2809]

thanks for response!

i noticed the actuator that controls hot/cold has a cracked gear in it, so im going to buy a new one. for now i put it back in to hold the door open to keep the a/c on, its also unplugged

the other one i removed (controls where the air is going, face, feet, windows) seems fine and in working order, but when i removed the cover off the actuator i think i accidently moved the gear off, so it will be out of sync now.

so...after buying the new one and installing the hot/cold one, and installing the direction actuator, i can recalibrate both of them by disconnection the a/c fuse, turning the truck off, plugging the a/c fuse back in and turn the truck on?

im pretty sure the new one will recalibrate for the hot/cold one, but im trying to save myself from buying a new direction actuator since i screwed up the sync on it.

[bighaas79]

these are good for stripping the gears and making clicking noises when they try to work, but i have had a couple "work" with assistance but wouldn't move the door on their own. I've also had a bunch just not work anymore. I've got a customer that only has 1 original actuator left in his truck, we've had to replace all the others in just the last year or so.