For 1990-2009 cars

# CLIMATE CONTROL TEMPERATURE UNSTABLE

#### VEHICLES AFFECTED: 1985-87 DEVILLE AND FLEETWOOD (C)

Some 1985 through 1987 De Ville and Fleetwood vehicles may exhibit A/C - heater temperature drift. This condition may be caused by insufficient air flow over the "in-car" temperature sensor, which may be caused by one or more of the following items:

1. Disconnected of kinked aspirator hose.

2. "In-car" temperature sensor opening in the upper I/P cover restricted by excess vinyl material.

3. Cadillac script restricting airflow over the in-car temperature sensor.

4. "In-car" sensor misaligned or touching sensor housing.

To repair this condition, complete the following steps:

1. With the climate control system operating at "high blower", right A/C duct off, observe if smoke is drawn around the Cadillac script at the right side of the upper I/P cover. If the smoke does not appear to be drawn into the sensor opening around the Cadillac script, insufficient aspirator operation may be suspected.

2. Remove the upper I/P cover as outlined in Section BC of the Cadillac Service Information Manual. During the removal operation, inspect the aspirator hose for disconnects and/or kinks which may restrict aspirator operation. If a disconnected or kinked hose is found, repair and retest as above.

3. Remove the "in-car" temperature from the upper I/P cover and inspect the thermistor alignment, the sensor should be centered in the hose opening and not touching any portion of the sensor housing.

4. Remove the two fasteners which retain the Cadillac script to the upper I/P cover. Inspect the sensor opening for vinyl/foam material restricting the cpening. Vinyl/foam material should be trimmed to the size as indicated by the metal reinforcement attached to the upper back of the I/P cover (Figure 1). If the vinyl/foam material is restricting the sensor opening, from the front side of the upper I/P cover, trim the material from the opening with a sharp knife or suitable tool using the metal reinforcement as a guide (Figure 1). Place the Cadillac script in the opening and observe the clearance between the back of the script and the I/P cover. If the clearance is less than 1/16", shim the script studs to obtain the proper clearance and install the script fasteners. Do not over torque the script fasteners.

5. Install the "in-car" temperature sensor to the upper I/P cover. Install the upper I/P cover to the instrument panel as outlined in Section 8C of the Cadillac Service Information Manual. In some cases the aspirator hose may be too long when properly routed and should be shortened to provide proper routing (Figure 2). Up to 16" may be removed to properly f i t the aspirator hose to eliminate kinking and provide proper air flow.

6. Road test the vehicle sufficiently to allow the system to stabilize and maintain a comfortable passenger compartment temperature. As the climate control system nears the set temperature, "tri-mode" operation will be observed. During the "tri-mode" air will be delivered from the defroster outlet, this should not be interpreted as temp drift. This is a normal condition for the system to provide a comfortable transition and maintain the set temperature.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.