This 2001 Cadillac Deville came in with the complaint that the driver’s side vent temperature stays hot all of the time. I checked codes in the instrument panel module and found a code B0408 stored for a fault in the air mix one actuator. With the B0408 code the problem could have easily have been that the air was stuck on cold all of the time.
There are two 7 mm headed screws that have to be removed to take the under dash panel out.
Once the screws are out the panel will drop down and pull out from under the dash. Then grab the knee bolster cover along the lower edge and pull it towards the seat. Work up the sides to the top. Pulling in the same manner to release the spring clips.
If you look above the firewall corner of the floor vent you can see part of the driver’s temperature or blend door actuator.
This picture was taken looking up from the gas pedal.
One of the screws that hold the actuator in place is directly above the floor vent duct work. I used a deep well 5.5 mm, 1/4″ drive socket and extension to remove that screw. The tip of the extension will come out to the rear of the brake pedal switches. Be careful to not move those two switches. If you do, your stoplights may not work properly and your transmission may not shift correctly.
The harness connector for this actuator only has two wires. A dark blue and a yellow wire.
The new actuator on the left and the old actuator on the right. The new actuator has the part number 89018380. The old actuator has a part number 52474878 on it. If you need one of these actuators please click here.
Accurate testing requires the use of a good scan tool and voltmeter but the actuator is almost always the culprit. If you want to do some testing, the a/c control panel will need to be removed. Start by gently prying down on the lower edge of the trim panel to release the clips. Once the clips are released start pulling the lower edge away from the dash and work your way up the sides. You will find the whole panel will seem to come loose except for the two top corners. Grab each corner as high as you can and pull straight out towards the seats. It may take a bit of pulling pressure to release the spring clips.
Now that the trim panel is removed, look closely at each side of the a/c control panel for the hold down latches. There are two on each side. Depress the latches and wiggle the a/c control panel from the dash.
A side view of the exposed latches.
After the control panel is removed you will notice that there are two harness connectors attached to the rear of the panel. The hook latches have to released by depressing the gray tabs at the wire side of the connector. With the hooks released, the connector bodies have to be wiggled/rocked and pulled to remove the harness connectors from the panel. Do not over flex as you could cause internal damage to the connector or the panel.
In the picture below I am pointing out the two wires that connect to the actuator, dark blue and yellow. Note that there are two yellow wires near next to the dark blue wire. One on either side. The correct yellow wire (B3) is the one one the left of the dark blue wire (B2).
The two wires at the actuator harness connector.If you feel the need or have other problems you can do a continuity test on the wires between the two connectors. Do not insert into the terminals that will distort them internally. These are micro 64 terminals and are easily damaged. Do your testing from the rear of the connectors.
As an added note. The control head applies 12 volt power on one wire and ground to the other for one direction of travel. It then reverses the polarity to change the direction of travel. When it has reached the desired position power (9.5-12 volts) is present on both wires and the actuator stalls If a hard code is stored the new actuator may not work until the code is cleared. Clearing the code and actuator recalibration can be done with a scan tool or by removing power to the a/c control panel. This can be done by removing the HVAC BAT fuse in the rear fuse box. It is a 10 amp fuse. Make sure the ignition is off and leave the fuse out for no less than 60 seconds. Install the fuse, turn the ignition on and wait for two minutes. Do Not Touch Anything during this two minutes. Switch the ignition off and then back on. Check system operation.
The tools that I need to do this repair. A 1/4″ ratchet, extension, 7 mm and 5.5 mm deep well sockets. I also used a flash light and a 1/4 cordless driver.
This repair is a bit tedious but not hard at all.