AIR CONDITIONING SYSTEM (for Manual Air Conditioning System) PTC Heater Circuit

DESCRIPTION

PTC heater relays are closed in accordance with signals from the air conditioning amplifier and power is supplied to the PTC heater installed on the radiator heater unit.

WIRING DIAGRAM

INSPECTION PROCEDURE

PROCEDURE

1. INSPECT FUSE (PTC NO. 1, PTC NO. 2, PTC NO. 3)

   
   

   1. Remove the PTC NO. 1, PTC NO. 2 and PTC NO. 3 fuses from the engine room No. 2 relay block.

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

      Standard resistance
      Tester Connection Condition Specified Condition PTC NO. 1 Always Below 1Ω PTC NO. 2 Always Below 1Ω PTC NO. 2 Always Below 1Ω

   
   

   NG

   REPLACE FUSE

   OK

2. INSPECT PTC HEATER RELAY

   
   

   1. 

      Remove the No. 1, No. 2 and No. 3 PTC heater relays from the engine room No. 2 relay block.

   2. Measure the resistance of the relays.

      Standard resistance
      Tester Connection Condition Specified Condition 3 - 5 when battery voltage is not applied to terminals 1 and 2 10 kΩ or higher 3 - 5 when battery voltage is applied to terminals 1 and 2 Below 1 Ω

   
   

   NG

   REPLACE PTC HEATER RELAY

   OK

3. CHECK HARNESS AND CONNECTOR (PTC HEATER RELAY - BODY GROUND)

   
   

   1. 

      Remove the No. 1, No. 2 and No. 3 PTC heater relays from the engine room No. 2 relay block.

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

      Standard resistance
      Tester Connection Condition Specified Condition No. 1 PTC heater relay terminal 2 - Body ground Always Below 1 Ω No. 2 PTC heater relay terminal 2 - Body ground Always Below 1 Ω No. 3 PTC heater relay terminal 2 - Body ground Always Below 1 Ω

   
   

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR

   OK

4. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER - PTC HEATER RELAY)

   
   

   1. 

      Remove the No. 1, No. 2 and No. 3 PTC heater relays from the engine room No. 2 relay block.

   2. Turn the ignition switch on (IG).

   3. When the PTC heater operating conditions are met (engine at idling speed or faster, ambient temperature is 10°C (50°F) or less, engine coolant temperature is 65°C (149°F) or less, set temperature switch is set to MAX HOT), turn the blower switch to the Lo setting.

   4. Measure the voltage according to the value(s) in the table below.

      Standard voltage
      Tester Connection Condition Specified Condition No. 1 PTC heater relay terminal 1 - Body ground Always 11 to 14 V No. 2 PTC heater relay terminal 1 - Body ground Always 11 to 14 V No. 3 PTC heater relay terminal 1 - Body ground Always 11 to 14 V

   
   

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR

   OK

5. CHECK HARNESS AND CONNECTOR (BATTERY - PTC HEATER RELAY)

   
   

   1. 

      Remove the No. 1, No. 2 and No. 3 PTC heater relays from the engine room No. 2 relay block.

   2. Measure the voltage according to the value(s) in the table below.

      Standard voltage
      Tester Connection Condition Specified Condition No. 1 PTC heater relay terminal 5 - Body ground Always 11 to 14 V No. 2 PTC heater relay terminal 5 - Body ground Always 11 to 14 V No. 3 PTC heater relay terminal 5 - Body ground Always 11 to 14 V

   
   

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR

   OK

6. CHECK HARNESS AND CONNECTOR (PTC HEATER RELAY - PTC HEATER)

   
   

   1. 

      Remove the No. 1, No. 2 and No. 3 PTC heater relays from the engine room No. 2 relay block.

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

      Standard resistance
      Tester Connection Condition Specified Condition No. 1 PTC heater relay terminal 3 - D40-2 (B) Always Below 1 Ω No. 2 PTC heater relay terminal 3 - D40-3 (B) Always Below 1 Ω No. 3 PTC heater relay terminal 3 - D40-1 (B) Always Below 1 Ω

   
   

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR

   OK

7. CHECK AIR CONDITIONING AMPLIFIER

   
   

   1. 

      Remove the air conditioning amplifier with its connectors still connected.

   2. Turn the ignition switch on (IG).

   3. When the PTC heater operating conditions are met (engine at idling speed or faster, ambient temperature is 10°C (50°F) or less, engine coolant temperature is 65°C (149°F) or less, set temperature switch is set to MAX HOT), turn the blower switch to the Lo setting.

   4. Measure the voltage according to the value(s) in the table below.

      Standard voltage
      Tester Connection Condition Specified Condition D33-3 (PTC1) - Body ground Always 11 to 14 V D33-22 (PTC2) - Body ground Always 11 to 14 V D33-4 (PTC3) - Body ground Always 11 to 14 V

   
   

   NG

   REPLACE AIR CONDITIONING AMPLIFIER

   OK

8. REPLACE PTC HEATER

   
   

   1. Replace the PTC heater Click here

   
   

   NEXT

9. CHECK PTC HEATER (OPERATION)

   
   

   1. Operate the PTC heater to check that functions properly.

      OK
      PTC heater function operates normally.

   
   

   NG

   PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE Click here

   OK

   END (PTC HEATER IS DEFECTIVE)