This 2002 Cadillac Deville came in with the complaint that the customer could not control the air flow modes. The control panel showed movement but the air flow was stuck on vent and the air flow was not very strong. A quick visual check of the mode actuator found that someone had unplugged it so that it would stay in one position. I plugged it back up and did some checking and determined the problem was indeed a faulty mode actuator assembly.
This repair should begin with the use of a Tech-2 or similar scan tool to properly diagnose the problem. Not many people have these tools at their disposal so here’s a trick to check it without a scan tool. You will of course have to get under the dash and have all wiring connected to do this. It is just easier to show how to use a quarter on a table. Place a quarter into the two slots in the shaft. Turn the key on and try to adjust the mode position in both directions. You should feel the shaft try to turn in at least one direction. If or when it stops before reaching its commanded position, use the quarter to rotate the shaft. If helping the actuator get past a sticking point is successful and the actuator comes to rest in its commanded position, you will have diagnosed an internal problem in the actuator. Again, this has to be done under the dash of course.
Now, once you have diagnosed a faulty mode actuator the fun begins. There are three ways to do this repair. The factory method involves removing the complete dash assembly. The second way is to remove the actuator from the mounting bracket and separate the cam gear from the actuator using a pry bar of some sort. I have never done it this way as it requires doing the same thing to the replacement part. It will void the warranty and you could wind up with two broken assemblies. Just my opinion. The third is the procedure I outline below.
Remove the lower dash cover and the vent duct. Sorry, no pictures of that. The next step is to remove the trim for the a/c controls and the radio. Unsnap it along the lower edge and the sides, then lift the bottom up and slid the two upper tabs out from under the wood grain trim panel.
There is a latch on either side of the radio that has to be released so that the radio can be removed. Do not disconnect the wiring for the radio unless you have the theft lock code. Carefully position the radio so it will hang without damaging the soft dash panels. Place a rag in between if needed.
With the radio out of the way, remove the 7 mm headed screw that is in the center of the picture below. Removing that screw will allow the duct to drop down enough so that you will be able to work more comfortably.
The radio is hanging, the screw for the duct work is removed and now you have to get under the dash. You have to lay as I am shown in the picture below. Depending on coordination level you may also have to be in the same relative position, only face down. Now the most important step. Connect and turn on a battery charger. Switch the ignition on. Turn the blower on high and if at all possible position the actuator to the vent position. Doing this will keep the doors in the proper position for installing a new actuator.
A 1/4″ palm ratchet and long 5.5 mm socket are my tools of choice. It can be done with a regular ratchet also.
You will need to go up and over the duct work that is shown in the picture below.
Some one had already worked on this one and the duct was split just below my wrist in the pictures below.
Unplug the harness connector and remove the mounting screws from the actuator assembly.
With all screws removed and the harness unplugged, gently pull the actuator assembly towards the steering column. Once it is free of the a/c box continue to maneuver it until you can pull it down and out of the dash.
Although the following picture is slightly blurry, I am using it to show the relative position of the levers in relation to the duct work that I am pulling down.
Both the picture above and below should be rotated 90 degrees counter clockwise for the proper orientation. All three of the white levers in the picture will fall off, if they are moved around too much. I they do fall off just put them back on as shown in the picture below. To double check the lever positions, all three of the male pegs should be as close together as possible.
The underside of the new actuator assembly.
The actuator may not be set properly when you get it, at least for this procedure. Pull the harness connector down and connect it to the actuator. Turn the key on and adjust the mode position on the a/c control head to the vent position. When the actuator stops, disconnect the wring from the actuator and turn the ignition off.
Maneuver the actuator back up into position and align the three pegs into the actuator cam gear. If all three do not drop into place do not be alarmed. Make sure that the lower one and the one closest to the firewall are in place. Put in a couple of screws but do not tighten them. Just snug them enough to hold the cam on the two pegs mentioned earlier.
Go around to the radio opening and use a long skinny screwdriver to align the last peg into the cam slots.
Leave the screwdriver in as a wedge and finish installing and tightening all of the screws.
To calibrate the actuator without a scan tool, remove the 15 amp IGN SW fuse in the rear under seat fuse box, position 29 (you can also disconnect the battery but memory settings will be lost). Remove the fuse for at least 60 seconds. Install the fuse and start the engine. Do not touch the a/c controls. Let the system run for about 4 minutes. Switch the ignition off for at least 10 seconds. Restart the engine and confirm the repair. To purchase this actuator please click here.
If you cannot flex backwards over the door sill and seat area, while resting your head between the brake and gas pedals, you cannot do this repair.
One more trick to make this job a little easier on the body. It is not very stylish but it does help protect the underside of your wrist when going over the floor duct work.