Home

Toyota Workshop

GSIC - Global Service Information Center

AIR CONDITIONING SYSTEM > PTC Heater Circuit

for Preparation Click here


DESCRIPTION

The PTC heater assembly is installed in the radiator in the heater unit and operates when engine coolant temperature is low and normal heater effectiveness is insufficient.
The A/C control assembly switches the circuit in the PTC relay and operates the PTC heater assembly when the operating conditions (cooling water temperature is below 65°C (149°F), setting temperature is MAX. HOT, ambient temperature is below 10°C (50°F) and blower switch is not OFF) are met.
The PTC heater assembly controls PTC heater lines by electric load or the amount of inverter with converter assembly (PCU) output. Therefore, troubleshooting should be performed with other electric components off.

WIRING DIAGRAM


E190298E02


INSPECTION PROCEDURE

1.INSPECT PTC HEATER ASSEMBLY


    E145133E16

  1. Remove the PTC heater assembly.

  1. Measure the resistance according to the value(s) in the table below.

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    A19-1 (B) - A20-1 (E)
    		Always
    		Below 1 Ω
    A19-2 (B) - A20-2 (E)
    		Always
    		Below 1 Ω
    A19-2 (B) - A20-1 (E)
    		Always
    		Below 1 Ω
    A19-3 (B) - A20-2 (E)
    		Always
    		Below 1 Ω

    Text in Illustration 
    *1
    		Component without harness connected
    (PTC Heater Assembly)



NG
REPLACE PTC HEATER ASSEMBLY (Click here)
OK


2.CHECK HARNESS AND CONNECTOR (PTC HEATER ASSEMBLY - BODY GROUND)


    E133943E02

  1. Measure the resistance according to the value(s) in the table below.

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    A20-1 (E) - Body ground
    		Always
    		Below 1 Ω
    A20-2 (E) - Body ground
    		Always
    		Below 1 Ω

    Text in Illustration 
    *1
    		Front view of wire harness connector
    (to PTC Heater Assembly)



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


3.CHECK HARNESS AND CONNECTOR (PTC HEATER ASSEMBLY - INTEGRATION RELAY)


    E134003E03

  1. Disconnect the PTC heater assembly connector.



    E190420E01

  1. Disconnect the engine room relay block and junction block (integration relay) connector.

  1. Measure the resistance according to the value(s) in the table below.

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    A19-1 (B) - 1H-10 (PTC1)
    		Always
    		Below 1 Ω
    A19-2 (B) - 1H-8 (PTC2)
    		Always
    		Below 1 Ω
    A19-3 (B) - 1H-9 (PTC3)
    		Always
    		Below 1 Ω
    A19-1 (B) - Body ground
    		Always
    		10 kΩ or higher
    A19-2 (B) - Body ground
    		Always
    		10 kΩ or higher
    A19-3 (B) - Body ground
    		Always
    		10 kΩ or higher

    Text in Illustration 
    *1
    		Front view of wire harness connector
    (to PTC Heater Assembly)
    *2
    		Front view of wire harness connector
    (to Engine Room Relay Block and Junction Block (Integration Relay))



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


4.CHECK HARNESS AND CONNECTOR (A/C AMPLIFIER - INTEGRATION RELAY)


    E177002E73

  1. Disconnect the A/C amplifier connector.



    E190419E01

  1. Disconnect the engine room relay block and junction block (integration relay) connector.

  1. Measure the resistance according to the value(s) in the table below.

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    L17-18 (PTC1) - 1G-17 (PTCA)
    		Always
    		Below 1 Ω
    L17-38 (PTC2) - 1G-26 (PTCB)
    		Always
    		Below 1 Ω
    L17-16 (PTC3) - 1G-25 (PTCC)
    		Always
    		Below 1 Ω
    L17-18 (PTC1) - Body ground
    		Always
    		10 kΩ or higher
    L17-38 (PTC2) - Body ground
    		Always
    		10 kΩ or higher
    L17-16 (PTC3) - Body ground
    		Always
    		10 kΩ or higher

    Text in Illustration 
    *1
    		Front view of wire harness connector
    (to A/C Amplifier)
    *2
    		Front view of wire harness connector
    (to Engine Room Relay Block and Junction Block (Integration Relay))



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


5.REPLACE INTEGRATION NO.1 RELAY

  1. Replace the integration relay (Click here).

    HINT:
    Since the integration relay cannot be inspected while it is removed from the vehicle, replace the integration relay with a new or a known good one and check that the condition returns to normal.

  1. Check if the same problem occurs again.

    OK:
    Same problem does not occur.



NG
PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE (Click here)
OK

END (INTEGRATION RELAY WAS DEFECTIVE)