The mode actuator is causing me problems with switching from the vent to the other vents, (defrost, floor, etc.). It will blow out the main vents, but when i turn the dial to have it come out the floor it will go to the defroster vents. It appears to be all electrical and no vaccuum lines. I looked under the hood and under the dash and started taking the dash apart a little bit before putting it back together without finding the actuator. I have service manual pages describing where the actuator is, but its not easy to get to for inspection. Can someone help me with finding a solution to fixing the actuator or if you know of another solution to fixing the problem I'm having. I have looked on youtube for help and couldn't locate anything specific. I have a 2002 Sierra 1500 SLT. Thank you.
HVAC Mode Actuator repair info needed
- Thread starter wojomar
- Start date
Molson02536
New member
The actuator is located under the driver's side of the dash, above the gas pedal area, and on the end of the heater a/c case. Then either by hand or using the tool, pull the retaining pin out that holds the heater duct in place.
The actuator is above the duct. In case you are wondering the piece in the duct is, it's the duct temperature sensor. There are two 5.5 mm headed screws that hold the actuator in place. The upper screw also holds the wiring harness retaining clip as well.
Try to set the old actuator to the same position as the new one before removing. To do this switch the ignition on and have someone depress the defroster button for you. While looking at the slot on the center shaft also have one hand on the ignition switch. Turn the ignition off just before the slot lines up with the appropriate hash mark.
If this is not possible for you just set the controls to the split defrost and floor position. This will make it easier to slip the actuator out. Lift the edge of the actuator, that is closest to the firewall away from the heater a/c case. It can take a good bit of patience and manipulation to remove the old actuator. So take your time and don't caveman it out.
This will enables the large cog to come out from under the pin on the white lever gear. Remember which slot it was in, the inner one. When the actuator is out of the way, you can see the two door levers, small black one to the left is for the defroster door and the larger white one with the gear teeth attached is for the vent / floor door.
Note the position of the actuator cog to the actuator motor. The actuators come prepositioned to allow for easier assembly. Do not connect the wiring to the actuator until the new actuator is installed. Slide the new actuator into place in the reverse order that you pulled it out.
Once it is generally back in place make sure that the peg on the back side of the white gear lever is in the inner slot of the actuator cog and while holding it gently in place reach up to the top side of the cog and make sure that the defroster lever is in its slot under the cog. Take your time and gently maneuver the actuator around until the actuator drops completely into place.
The two door lever pins have to be lined up. The actuator has to be lined up with the two mounting bosses, the center rings on the actuator cog and the heater a/c case also have to be lined up. Remember patience and gentle maneuvering and it will drop that last little 1/4" to 3/8" to the mounting base. Do not force or use the screws to draw it down. You will likely break the actuator or have the actuator jammed at the very least.
If your truck has auto a/c controls. The part and the basic repair are the same whether it has manual or auto controls. Difference is to preset the controls to the split defrost / floor position before removing the old actuator.
If you'll need is a small screwdriver or the edge of a quarter to rotate the actuator into the correct position if you are manually assisting the actuator. This must be done within the first minute or two of switching the ignition on. The system will try to adjust to the commanded position for a minute and then stops trying and the motor will not be able to be assisted. The ignition will need to be turned off for at least ten seconds and then back on for another attempt.
To perform a recalibration of the newly installed actuator, used a Tech 2 scan tool. If you do not have a scan tool you have two choices. Remove the HVAC fuse for one minute or disconnect the battery for one minute. After the fuse is installed or the battery is reconnected, start the engine and let it run for at least one minute (I prefer the old time of 4 minutes). DO NOT TOUCH the a/c controls during this time. Turn the ignition off for at least ten seconds. Restart the engine and check the a/c operation.
Good luck and keep us posted.
Molson02536