PTC Heater Circuit

AIR CONDITIONING: AIR CONDITIONING SYSTEM: PTC Heater Circuit

PTC Heater Circuit

DESCRIPTION

The PTC heater is installed in the radiator in the heater unit and operates when cooling water temperature is low and normal heater effectiveness is insufficient.
The air conditioning amplifier switches the circuit in the PTC relay and operates the PTC heater when the operating conditions (cooling water temperature is below 55°C (131°F), setting temperature is MAX. HOT, air outlet damper position is FOOT or FOOT/DEF, and blower switch is not OFF) are met.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. INSPECT FUSIBLE LINK (HTR SUB1, HTR SUB2)




(a) Remove the fusible link from the engine room relay block and junction block No. 1.




(b) Check if the fusible link is melted.
OK:
The point indicated by "A" is not melted.
(c) Install the fusible link to the engine room relay block and junction block No. 1 with the nut.
NG -- REPLACE FUSIBLE LINK (HTR SUB1, HTR SUB2)
OK -- Continue to next step.
2. INSPECT PTC HEATER RELAY




(a) Remove the PTC heater relay from the engine room relay block No. 3.
(b) Measure the resistance according to the value(s) in the table below.
Standard resistance:





(c) Install the PTC heater relay to the engine room relay block No. 3.
NG -- REPLACE PTC HEATER RELAY
OK -- Continue to next step.
3. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER - BODY GROUND)




(a) Disconnect the connector from the A/C amplifier.
(b) Measure the resistance according to the value(s) in the table below.
Standard resistance:






NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
4. INSPECT AIR CONDITIONING AMPLIFIER (PTC1, PTC2)




(a) Reconnect the connector to the A/C amplifier.
(b) Measure the voltage according to the value(s) in the table below.
Standard voltage:






NG -- REPLACE AIR CONDITIONING AMPLIFIER
OK -- Continue to next step.
5. CHECK HARNESS AND CONNECTOR (BATTERY - PTC HEATER)




(a) Disconnect the connector from the PTC heater.
(b) Measure the voltage according to the value(s) in the table below.
Standard voltage:






NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE