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Automatic A/c-Heater Systems: Overview Lexus LS III

Automatic HVAC System ~375 words

DESCRIPTION

WARNINGTo avoid injury from accidental air bag deployment, read and carefully follow all SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM procedures in AIR BAG SYSTEM SAFETY article in GENERAL SERVICING.

Note. When battery is disconnected, radio will go into anti-theft protection mode. Obtain radio anti-theft protection code from owner prior to servicing vehicle.

All A/C-heating functions are controlled automatically by A/C Electronic Control Unit (ECU) located on passenger side of blower unit. Independent temperature controls are available for driver and passenger temperature adjustment. Manual controls allow driver to select preferred air distribution mode and temperatures. In addition to normal A/C system components, the system includes various servomotors, controls, and sensors. A smoke sensor is included with rear A/C or air purifier and is used to improve air quality. The A/C system has self-diagnostic capabilities.

A refrigerant gas and liquid separator (modulator) has replaced the receiver-drier. Modulator is integrated into one end of condenser. A replaceable drier bag and filter are located inside the modulator.

No Blower Motor Operation

  1. Check IG power source circuit. See «IG POWER SOURCE CIRCUIT»(ref-99101-S41436495502001061800000) under SYSTEM TESTS.
  2. Check ACC power source circuit. See «ACC POWER SOURCE CIRCUIT»(ref-99101-S32976624232001061800000) under SYSTEM TESTS.
  3. Check front blower motor circuit. See «BLOWER MOTOR CIRCUIT»(ref-99101-S10101323542001061800000) under SYSTEM TESTS.

No Rear Blower Motor Operation

  1. Check ACC power source circuit. See «ACC POWER SOURCE CIRCUIT»(ref-99101-S32976624232001061800000) under SYSTEM TESTS.
  2. Temporarily substitute known-good rear A/C amplifier, then retest system.
  3. Check body ECU. See appropriate MULTIPLEX CONTROL SYSTEMS article in ACCESSORIES & EQUIPMENT.
  4. Check rear blower motor circuit. See «BLOWER MOTOR CIRCUIT»(ref-99101-S10101323542001061800000) under SYSTEM TESTS.
  5. Check rear blower motor resistor. See «BLOWER MOTOR CIRCUIT»(ref-99101-S10101323542001061800000) under SYSTEM TESTS.

Cooling Fan Operational Check

  1. Remove engine air intake duct. Disconnect cooling fan 2-pin connector. Connect an ammeter in series between positive battery terminal and cooling fan motor terminal No. 1. Connect negative battery terminal to cooling fan terminal No. 2.
  2. Fan should operate smoothly. Ammeter should read 9.2-11.0 amps at 68°F (20°C). If operation is as specified, go to next step. Replace cooling fan motor if operation is not as specified.
  3. Disconnect cooling fan ECU 3-pin connector. Measure voltage between cooling fan motor harness connector terminals No. 1 (Brown wire) and No. 3 (White/Blue wire).
  4. If voltage is 9.0-14.0 volts, replace cooling fan ECU. If voltage is not 9.0-14.0 volts, check FAN fuse (50-amp) located in engine compartment fusible link block, fan relay and wiring harness. See «WIRING DIAGRAMS»(ref-99101-S32973477022001061800000) .

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