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Home >> Lexus >> 2008 >> LS 600hL >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Air Conditioning >> Air Conditioning System >> PTC Heater Circuit >> Inspection Procedure

Inspection Procedure

  1. INSPECT FUSE (PTC HTR1, PTC HTR3, PTC HTR) 
    1. Remove the PTC HTR1 and PTC HTR3 fuses from the engine room No 4 relay block, and PTC HTR H-fuse from the engine room No. 1 junction block
    2. Measure the resistance according to the value(s) in the table below.

      Standard resistance 

      TESTER CONNECTOR SPECIFIED CONDITION CHART

      Tester Connection Condition Specified Condition
      PTC HTR1 fuse Always Below 1 Ω
      PTC HTR3 fuse
      PTC HTR H-fuse

    NG: REPLACE FUSE 

    OK: Go to Next Step 

  2. CHECK AIR CONDITIONING AMPLIFIER 
    1. Remove the air conditioning amplifier with its connectors still connected (see REMOVAL  )
    2. Measure the voltage according to the value(s) in the table below

      Standard voltage 

      TESTER CONNECTOR SPECIFIED CONDITION CHART

      Tester Connection Condition Specified Condition
      L76-27 (PTC1) - Body ground Power switch ON (IG)
      Temperature setting: MAX. HOT
      MODE switch: FOOT
      Engine coolant temperature: 55°C (131°F) or lower
      Blower switch: OFF      		 11 to 14 V
      L76-35 (PTC3) - Body ground
      Fig 1: Identifying Terminals Of L76 Air Conditioning Amplifier Connector
      G05774376Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPLACE AIR CONDITIONING AMPLIFIER  (See REMOVAL  )

    OK: Go to Next Step 

  3. INSPECT PTC HEATER RELAY (PTC HTR1, PTC HTR3) 
    1. Remove the PTC heater relays from the No. 4 relay block.
    2. Measure the resistance according to the value(s) in the table below.

      Standard resistance 

      TESTER CONNECTOR SPECIFIED CONDITION CHART

      Tester Connection Condition Specified Condition
      3 - 5 When battery voltage is not applied between terminals 1 and 2 10 kΩ or higher
      When battery voltage is applied to terminals 1 and 2 Below 1 Ω
      Fig 2: Identifying Terminals Of PTC Heater Relays
      G05774377Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPLACE PTC HEATER RELAY 

    OK: Go to Next Step 

  4. CHECK HARNESS AND CONNECTOR (PTC HEATER RELAY - PTC HEATER) 
    1. Remove the PTC heater relays from the No. 4 relay block.
    2. Disconnect the L40 PTC heater connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard resistance 

      TESTER CONNECTOR SPECIFIED CONDITION CHART

      Tester Connection Condition Specified Condition
      PTC HTR1 terminal 3 - L40-1 (B) Always Below 1 Ω
      PTC HTR3 terminal 3 - L40-3 (B)
      Fig 3: Identifying Terminals Of L40 PTC Heater Connector
      G05774378Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: Go to Next Step 

  5. CHECK PTC HEATER 
    1. Disconnect the L40 and L41 PTC heater connectors
    2. Measure the resistance according to the value(s) in the table below

      Standard resistance 

      TESTER CONNECTOR SPECIFIED CONDITION CHART

      Tester Connection Condition Specified Condition
      L40-1 (B) - L41-1 (E) Always Below 1 Ω
      L40-3 (B) - L41-2 (E)
      Fig 4: Identifying Terminals Of L40 PTC Heater Connector
      G05774379Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPLACE PTC HEATER  (See REMOVAL  )

    OK: Go to Next Step 

  6. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER - BODY GROUND) 
    1. Disconnect the L76 air conditioning amplifier connector.
    2. Measure the resistance according to the value(s) in the table below

      Standard resistance 

      TESTER CONNECTOR SPECIFIED CONDITION CHART

      Tester Connection Condition Specified Condition
      L76-27 (PTC1) - Body ground Always Below 1 Ω
      L76-35 (PTC3) - Body ground
      Fig 5: Identifying Terminals Of L76 Air Conditioning Amplifier Connector
      G05774380Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: REPLACE AIR CONDITIONING AMPLIFIER  (See REMOVAL  )

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