CLIMATE CONTROL TEMP. DRIFT REVISED SERVICE PROCEDURE

SUBJECT: CLIMATE CONTROL TEMPERATURE DRIFT

MODELS AFFECTED: 1985-1991 DE VILLES AND FLEETWOODS

This bulletin supersedes bulletin T-87-103 which should be discarded. The 1988-1991 model year vehicles have been added to this bulletin and the procedure has been revised.

Some 1985-1991 DeVilles and Fleetwoods 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:

o Disconnected or kinked aspirator hose. o In-car temperature sensor opening in the upper I/P cover restricted by excess vinyl material. o "Cadillac" script restricting air flow over the in-car temperature sensor. o In-car sensor misaligned or touching sensor housing.

To repair this condition use the following procedure:

1. Remove the upper I/P cover as outlined in Section 8C 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.

2. Remove the in-car temperature sensor 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. Refer to Figure 1A. Should the sensor be severely mislocated, as seen in Figure 1B, it should be replaced rather than relocated.

3. 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 opening. 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. Refer to Figure 2A. 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. Refer to Figure 2B. 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", replace the script with P/N 25602888 to obtain proper clearance and install the script fasteners. DO NOT OVER-TORQUE SCRIPT FASTENERS.

4. 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. Refer to Figure 3. Up to 16" may be removed to properly fit the aspirator hose to eliminate kinking and provide proper air flow.

5. 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 in the 1985-1988 vehicles. During "tri-mode" air will be delivered from the defroster outlet. The 1989-1991 vehicles will enter "bi-level" as the system nears its set temperature and will deliver air out of the heater and A/C outlets. This is a normal condition for the system to provide a comfortable transition and maintain the set temperature.

6. If the vehicle still exhibits an A/C heater temperature drift condition, contact CAD-STAR for additional assistance.

Parts are currently available from GMSPO.

For warranty purposes use Labor Operation T6219 at .7 hour for trimming excess material, shortening aspirator hose, and/or replacing script. Add .3 hour to replace or relocate in-car temperature sensor.

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.