DESCRIPTION
WIRING DIAGRAM
INSPECTION PROCEDURE
INSPECT FUSE (LH-IG, GLW PLG1, GLW PLG2)
INSPECT RELAY (GLW RLY1, GLW RLY2)
CHECK HARNESS AND CONNECTOR (A/C AMPLIFIER - BATTERY)
INSPECT AIR CONDITIONING AMPLIFIER
INSPECT HEATER BLOWER WIRE
INSPECT WATER BY-PASS GLOW PLUG
AIR CONDITIONING SYSTEM - PTC Heater Circuit
DESCRIPTION
The GLW RLY turns on when it receives a signal from the A/C amplifier. As a result, power is supplied to the heater glow plug.
WIRING DIAGRAM
INSPECTION PROCEDURE
| 1.INSPECT FUSE (LH-IG, GLW PLG1, GLW PLG2) |
Remove the LH-IG fuse from the cowl side J/B LH.
Remove the GLW PLG1 and GLW PLG2 fuses from the engine room R/B and J/B No. 1.
Measure the resistance according to the value(s) in the table below.
- Standard resistance:
| Tester Item | Condition | Specified Condition |
| LH-IG fuse | Always | Below 1 Ω |
| GLW PLG1 fuse | Always | Below 1 Ω |
| GLW PLG2 fuse | Always | Below 1 Ω |
| 2.INSPECT RELAY (GLW RLY1, GLW RLY2) |
Remove the GLW RLY1 and GLW RLY2 relays from the engine room R/B and J/B No. 1.
Measure the resistance according to the value(s) in the table below.
- Standard resistance:
| Tester Connection | Condition | Specified Condition |
| 3 - 5 | Always | 10 kΩ or higher |
| 3 - 5 | When battery voltage is applied to terminals 1 and 2 | Below 1 Ω |
| 3.CHECK HARNESS AND CONNECTOR (A/C AMPLIFIER - BATTERY) |
Disconnect the connector from the A/C amplifier.
Turn the engine switch on (IG).
Measure the voltage according to the value(s) in the table below.
- Standard voltage:
| Tester Connection (Symbols) | Condition | Specified Condition |
| J58-4 (HTR2) - Body ground | Engine switch on (IG) | 10 to 14 V |
| J58-23 (HTR1) - Body ground | Engine switch on (IG) | 10 to 14 V |
| | REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
|
| 4.INSPECT AIR CONDITIONING AMPLIFIER |
Reconnect the connector to the A/C amplifier.
Measure the voltage according to the value(s) in the table below.
- Standard voltage:
| Tester Connection | Condition | Specified Condition |
| J58-4 (HTR2) - Body ground | Engine switch on (IG) | 10 to 14 V |
| J58-4 (HTR2) - Body ground | Engine switch on (IG)
While the PTC operating conditions are met (engine is running at 850 rpm or more, ambient temperature is 0°C (32°F) or less, engine coolant temperature is 69°C (156°F) or less, and A/C switch setting is MAX HOT), turn the blower switch to the LO setting. | Below 1 V |
| J58-23 (HTR1) - Body ground | Engine switch on (IG) | 10 to 14 V |
| D47-2 - Body ground | Engine switch on (IG)
While the PTC operating conditions are met (engine is running at 850 rpm or more, ambient temperature is 0°C (32°F) or less, engine coolant temperature is 69°C (156°F) or less, and A/C switch setting is MAX HOT), turn the blower switch to the LO setting. | Below 1 V |
| | REPLACE AIR CONDITIONING AMPLIFIER |
|
|
| 5.INSPECT HEATER BLOWER WIRE |
Remove the grommets and nuts of the water by-pass glow plugs.
Turn the engine switch on (IG).
Perform Active Test by referring to the table below.
Active Test / Air Conditioner:| Item | Test Details / Display (Range) | Diagnostic Note |
Electric Heater 1
(Heater 1) | Electric Heater 1 / OFF, ON | - |
Electric Heater 2
(Heater 2) | Electric Heater 2 / OFF, ON | - |
Measure the voltage according to the value(s) in the table below.
- Standard voltage:
| Tester connection | Condition | Specified condition |
| 1 - Body ground | Perform Active Test / HEATER 1 (Electric Heater 1): ON | 10 to 14 V |
| 2 - Body ground | Perform Active Test / HEATER 2 (Electric Heater 2): ON | 10 to 14 V |
| | REPAIR OR REPLACE HEATER BLOWER WIRE |
|
|
| 6.INSPECT WATER BY-PASS GLOW PLUG |
Remove the water by-pass glow plug.
Measure the resistance according to the value(s) in the table below.
- Standard resistance:
- Below 1 Ω
| | REPLACE WATER BY-PASS GLOW PLUG |
|
|
| OK | |
| |
| PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE |
|
LEXUS IS250, IS220d / GSE20 ALE20
