A/C Control Assembly - Troubleshooting & Service Parts

REF: HEATING & AIR CONDITIONING

NO.: AC005-96

DATE: JULY 19, 1996

MODEL: LS 400

TITLE: 1990 - 1994 LS 400 A/C CONTROL ASSEMBLY SERVICE PARTS








To allow repairs to the A/C Control Assembly, service parts are now available, The following information on parts and troubleshooting will aid you in addressing complaints with the LCD display, night illumination or switch indicators.





TROUBLESHOOTING:

Use the matrix chart as a guide to repairs. Verify necessary inputs to the A/C Control Assembly from the vehicle prior to disassembly. Use the repair manual, A/C system section, to validate inputs such as B+, ILL+, ground, etc.

NOTE:
If the symptom still exists after the suspect areas have been tested and found not to be faulty, replace the amplifier.








AIR CONDITIONING CONTROL DISASSEMBLY:





REPLACEMENT PROCEDURE FOR NIGHT ILLUMINATION BULB AND LCD ILLUMINATION BULB:

COMPONENT IDENTIFICATION:








A minor change to the control panel was made for the '93 model year, therefore the '90-'92 model year control panels differ from the '93-'94 model year panels. Use the illustrations to properly identify the components.

INSPECTION PROCEDURE:





1. Bulb Circuit

a. Perform the following test on suspect LCD or Night Illumination Bulbs. Check for continuity as shown. Replace the bulb if there is no continuity.

b. With known good bulbs installed, check for continuity between the following terminals of the illumination circuit. Replace the control panel if there is no continuity.





2. Switch Circuit

Switch Continuity Inspection:





Check that there is continuity between the terminals while the switch is pressed.

If there is no continuity between even one pair of terminals, replace the control panel.





3. Indicator Lamp Circuit

Indicator Lamp Circuit Inspection:

Connect two 1.5v dry cell batteries in series. Using the table, check that each suspect indicator lights up.

NOTE:
Since the indicator lamps are LEDs, do not mix the "+" and "-" terminals of the test batteries or apply power to them for more than 3 seconds at a time.

If a suspect LED does not light up when tested, replace the control panel.








CONTROL PANEL INNER CIRCUITS:

PART NUMBER INFORMATION:








If necessary, use the information under Component Identification in this TSB to properly identify these components:





WARRANTY INFORMATION: