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PTC Heater Circuit








AIR CONDITIONING: AIR CONDITIONING SYSTEM: PTC Heater Circuit

PTC Heater Circuit

DESCRIPTION

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

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. INSPECT FUSE (A/C, HTR SUB1, HTR SUB2)
(a) Remove the A/C fuse from the main body ECU.
(b) Remove the HTR SUB1 and HTR SUB2 fuses from the engine room relay block.
(c) Measure the resistance.
Standard resistance:





(d) Reinstall the A/C fuse.
(e) Reinstall the HTR SUB1 and HTR SUB2 fuses.
NG -- REPLACE FUSE
OK -- Continue to next step.
2. INSPECT NO. 3 HEATER CONTROL KNOB




(a) Remove the No. 3 heater control knob.
(b) Measure the resistance.
Standard resistance:





(c) Reinstall the No. 3 heater control knob.
NG -- REPLACE NO. 3 HEATER CONTROL KNOB
OK -- Continue to next step.
3. CHECK HARNESS AND CONNECTOR (MAIN BODY ECU - AIR CONDITIONING AMPLIFIER)




(a) Disconnect the E6 No. 3 heater control knob connector.
(b) Measure the voltage.
Standard voltage:





(c) Reconnect the No. 3 heater control knob connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
4. CHECK HARNESS AND CONNECTOR (No. 3 HEATER CONTROL KNOB - AIR CONDITIONING AMPLIFIER)




(a) Disconnect the E6 No. 3 heater control knob connector.
(b) Disconnect the E9 air conditioning amplifier connector.
(c) Measure the resistance.
Standard resistance:





(d) Reconnect the No. 3 heater control knob connector.
(e) Reconnect the air conditioning amplifier connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
5. INSPECT AIR CONDITIONING AMPLIFIER




(a) Remove the air conditioning amplifier with its connectors still connected.
(b) Turn the ignition switch ON.
(c) 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, and No. 3 heater control knob setting is MAX HOT), turn the blower switch to the Lo setting.
(d) Wait 30 seconds.
(e) Measure the voltage.
Standard voltage:





(f) Reinstall the air conditioning amplifier.
NG -- REPLACE AIR CONDITIONING AMPLIFIER
OK -- Continue to next step.
6. INSPECT PTC HEATER RELAY (HTR SUB1, HTR SUB2, HTR SUB3)




(a) Remove the HTR SUB1 relay from the engine room relay block.
(b) Remove the HTR SUB2 and HTR SUB3 relays from the engine room sub relay block.
(c) Measure the resistance.
Standard resistance:





(d) Reinstall the HTR SUB1 relay.
(e) Reinstall the HTR SUB2 and HTR SUB3 relays.
NG -- REPLACE PTC HEATER RELAY
OK -- Continue to next step.
7. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER - PTC HEATER RELAY)




(a) Remove the HTR SUB1 relay from the engine room R/B.
(b) Remove the HTR SUB2 and HTR SUB3 relays from the engine room R/B No. 2.
(c) Turn the ignition switch ON.
(d) 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, and No. 3 heater control knob setting is MAX HOT), turn the blower switch to the Lo setting.
(e) Wait 30 seconds.
(f) Measure the voltage.
Standard voltage.:





(g) Reinstall the HTR SUB1 relay.
(h) Reinstall the HTR SUB2 and HTR SUB3 relays.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
8. CHECK HARNESS AND CONNECTOR (PTC HEATER RELAY - BODY GROUND)




(a) Remove the HTR SUB1 relay from the engine room R/B.
(b) Remove the HTR SUB2 and HTR SUB3 relays from the engine room R/B No. 2.
(c) Measure the resistance.
Standard resistance:





(d) Reinstall the HTR SUB1 relay.
(e) Reinstall the HTR SUB2 and HTR SUB3 relays.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
9. INSPECT PTC HEATER ASSEMBLY




(a) Disconnect the A17 PTC heater assembly connector.
(b) Measure the resistance.
Standard resistance:





(c) Reconnect the PTC heater assembly connector.
NG -- REPLACE PTC HEATER ASSEMBLY
OK -- Continue to next step.
10. CHECK HARNESS AND CONNECTOR (BATTERY - PTC HEATER RELAY)




(a) Remove the HTR SUB1 relay from the engine room R/B.
(b) Remove the HTR SUB2 and HTR SUB3 relays from the engine room R/B No. 2.
(c) Measure the voltage.
Standard voltage:





(d) Reinstall the HTR SUB1 relay.
(e) Reinstall the HTR SUB2 and HTR SUB3 relays.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
11. CHECK HARNESS AND CONNECTOR (PTC HEATER RELAY - PTC HEATER ASSEMBLY)




(a) Remove the HTR SUB1 relay from the engine room R/B.
(b) Remove the HTR SUB2 and HTR SUB3 relays from the engine room R/B No. 2.
(c) Disconnect the A17 PTC heater assembly connector.
(d) Measure the resistance.
Standard resistance:





(e) Reinstall the HTR SUB1 relay.
(f) Reinstall the HTR SUB2 and HTR SUB3 relays.
(g) Reconnect the PTC heater assembly connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE AIR CONDITIONING AMPLIFIER
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