Climate Control - Temperature Drift

Bulletin No. T 87-103
File in Group 1
Number 34
Corp. Ref. No. 711202
Date May '87
SUBJECT: CLIMATE CONTROL TEMPERATURE DRIFT

MODELS AFFECTED: 1985-1987 DE VILLES AND FLEETWOODS
Some 1985-1987 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 or kinked aspirator hose.
2. "In-car" temperature sensor opening in the upper I/P cover restricted by excess vinyl material.
3. Cadillac script restricting air flow over the in-car temperature sensor.
4. "In-car" sensor mis-aligned 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 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 re-test as above.

3. 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.

FIGURE 1 - I/P Cover And Assembly:

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 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 (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.

FIGURE 2 - Aspirator Hose:

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 fit 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 "tri-mode", air will be delivered from the defroster outlet, this should not be interpreted as temperature drift. This is a normal condition for the system to provide a comfortable transition and maintain the set temperature.

For warranty purposes, use Labor Operation number T6219 for .7 hour.