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HOMESERVICE MANUALSCHRYSLER1999LHSREPAIR AND DIAGNOSISHEATING, VENTILATION & A/C (HVAC)HVAC CONTROL SYSTEMSHVAC SYSTEMS - AUTOMATICTESTINGTEST 1A: IDENTIFYING ATC SYSTEM PROBLEMS
1999 Chrysler LHS

Test 1A: Identifying ATC System Problems

1999 Chrysler LHSSECTION Test 1A: Identifying ATC System Problems
  1. Turn ignition off. Connect scan tool to Data Link Connector (DLC). See Fig 1 . Using scan tool and the most current diagnostic program cartridge, ensure there is communication with Body Control Module (BCM) and Powertrain Control Module (PCM). If scan tool has a blank screen, go to next step. If any other communication problem exists, go to appropriate BODY CONTROL COMPUTER article in ACCESSORIES & EQUIPMENT. If there are no communication problems, go to step  7 .
  2. Turn ignition off. Disconnect scan tool from DLC. Check connector for an open, loose, or disconnected terminal. Repair as necessary.
  3. Using a DVOM, ensure that there is continuity between ground and DLC terminals No. 4 (Black wire) and No. 5 (Black/Light Green wire). If continuity is present, go to next step. If continuity is not present, repair wire(s) as necessary.
  4. Using a DVOM, check voltage at DLC terminal No. 16 (Pink wire). If battery voltage is not present, go to next step. If battery voltage is present, go to step  6 .
  5. If battery voltage is not present, check fuse No. 19 (10-amp) located in junction block, behind end cover at left side of instrument panel. See Figure and Figure . Replace fuse if blown. If fuse blows again, repair DLC battery feed circuit as necessary.
  6. Substitute scan tool cable with a known-good cable. If scan tool screen is no longer blank and scan tool is functioning properly, go to next step. If scan tool screen is still blank, replace defective scan tool. If there are no communication problems, go to next step.
  7. Using scan tool, select ENGINE and then READ DTCS. If scan tool does not display any PCM DTCs, go to next step. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE, if any of the following A/C-heater system related PCM DTCs are displayed:
    • ECT SENSOR VOLTAGE TOO LOW
    • ECT SENSOR VOLTAGE TOO HIGH
    • A/C PRESSURE SENSOR VOLTAGE TOO HIGH
    • A/C PRESSURE SENSOR VOLTAGE TOO LOW
    • LOW SPEED FAN CONTROL RELAY CIRCUIT
    • HIGH SPEED FAN CONTROL RELAY CIRCUIT
    • A/C CLUTCH RELAY CIRCUIT
    • ENGINE IS COLD TOO LONG
  8. Using scan tool, select BODY SYSTEM, BODY COMPUTER, SENSORS and then IGNITION VOLTAGE. Turn ignition on. If battery voltage is displayed, go to next step. If battery voltage is not displayed, go to appropriate BODY CONTROL COMPUTER article in ACCESSORIES & EQUIPMENT.
  9. Using scan tool, select BODY SYSTEM, BODY COMPUTER, and then READ DTCS. If ATC system related BCM DTCs are not present, go to next step. If ATC system related BCM DTCs are present, go to TEST 1B: IDENTIFYING ATC SYSTEM BCM DIAGNOSTIC TROUBLE CODES  .
  10. Using scan tool, select BODY SYSTEM, and then AUTO TEMP CTRL. If scan tool does not display NO RESPONSE, go to next step. If scan tool displays NO RESPONSE, see appropriate BODY CONTROL COMPUTER - VEHICLE COMMUNICATIONS article in ACCESSORIES & EQUIPMENT.
  11. If no BCM DTCs exist and any ATC control head switch is inoperative, go toTEST 2A: INOPERATIVE ATC CONTROL HEAD SWITCH  . If no BCM DTCs exist and recirculation door is inoperative, go to TEST 12A: RECIRCULATION DOOR ACTUATOR STALL TEST FAILURE  .
  12. If no BCM DTCs exist and there is a problem with A/C clutch operation, go to TEST 14A: COMPRESSOR CLUTCH CIRCUIT  . If no BCM DTCs exist and temperature control/blend air door is inoperative, go to TEST 15A: INOPERATIVE TEMPERATURE/BLEND AIR DOOR  .
  13. If no BCM DTCs exist and blower motor is inoperative, go to TEST 16A: INOPERATIVE BLOWER MOTOR  . If no BCM DTCs exist and blower motor speed(s) are incorrect, go to TEST 17A: INCORRECT BLOWER MOTOR SPEEDS  .
  14. If no BCM DTCs exist and there is a problem with ATC control head illumination, but instrument panel lights operate properly, go to TEST 18A: ATC CONTROL HEAD ILLUMINATION  . If no BCM DTCs exist and mode door is inoperative, go to TEST 19A: INOPERATIVE MODE DOOR  . If no BCM DTCs exist and temperature control is incorrect in sun or shade, go to TEST 21A: INCORRECT TEMPERATURE CONTROL IN SUN OR SHADE  .
  15. If instrument panel lights do not operate properly, see ILLUMINATION/INTERIOR LIGHTS article in ACCESSORIES & EQUIPMENT. If rear window defogger is inoperative, see appropriate REAR WINDOW DEFOGGER article in ACCESSORIES & EQUIPMENT.
Fig 1: Locating Data Link Connector (DLC)
G98A04003Courtesy of CHRYSLER CORP.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.