Mk. III Air Conditioning - Revised
88jaguar01AIR CONDITIONING
SECTION: 82
No: 6
Model: XJ-S Date: JANUARY, 1988
KEY POINTS: Mk. III AIR CONDITIONING
In order to achieve a more consistent temperature blend between footwell and dashboard air (when A/C is in operation), the supplier jig set position of the rotary flaps has been revised from VIN No. 135721.
To improve the footwell/dashboard air blend on vehicles manufactured before this date, the following repair procedure should be followed:
FIGURE 1:
REPAIR PROCEDURE
1. Remove the passenger's and driver's side underdash trim to gain access to the lower feedback potentiometer, and ECU, (R/H side Fig. 1.).
FIGURE 2:
2. Run engine with the air conditioning/heater system engaged until the normal operating temperature is reached. Ensure all manually operated dashboard vents are open.
3. Set the fan speed switch to normal and the temperature demand control switch to the mid position. (Fig. 2).
Move the face level differential control to the minimum differential position, i.e., full heat position ("C" Fig. 2).
4. Select the Manual mode by pulling the temperature demand switch forwards, (Fig. 2). This will automatically adjust the rotary flaps to a pre-determined position and maintains consistency of the footwell/dashboard air temperatures during the adjustment procedures.
NOTE: The following steps require the use of the Jaguar Diagnostic System.
FIGURE 3:
5. With the JDS in the voltage multimeter mode (connect battery cable to secure ground) probe connector SAC 4 PIN 5 Brown wire, (Fig. 3, A), at the ECU and simultaneously adjust the temperature demand switch until the millivolts reading shown on the JDS is 1410 to 1470.
6. Using air conditioning test system or temperature pyrometer equipment with the engine running at approximately 1,500 RPM, observe the temperature difference at the dashboard side vent and the footwell outlet, (on same side of vehicle). The temperature difference should be 32 C - 53.6 C with the dashboard level cooler than the lower level. For example:
DASHBOARD FOOTWELL DIFFERENCE
75.2 F (24 C) 96.8 F (36 C) 53.6 F (12 C)
82.4 F (28 C) 95.0 F (35 C) 7.0 F ( 7 C)
NOTE: When positioning temperature monitoring equipment probes, ensure they are positioned in the outlet airflows so an average temperature reading is taken.
If the temperature differential does not fall within the specifications, the adjustment procedure is as follows:
1. Slacken the lower feedback potentiometer securing screws.
2. Adjust potentiometer clockwise for cooler air at the footwell outlets.
3. Adjust counterclockwise for warmer air at the footwell outlets.
FIGURE 4:
NOTE: If the potentiometer is difficult to turn, the harness securing tie strap can be removed, (Fig. 4, A).
CAUTION: The slightest adjustment of the potentiometer results in a significant change in the position of the lower rotary flap.