Mitsubishi Lancer (4A9 engine). Manual — part 299

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-77

INSPECTION PROCEDURE 14: The PTC heater does not work. <Vehicles with PTC heater>

PTC Heater Circuit

PTC
HEATER
RELAY3

PTC
HEATER
RELAY1

GLOW
CONTROL
RELAY

PTC
HEATER
RELAY2

PTC
HEATER

A/C-ECU

A/C-ECU

IGNITION
SWITCH (IG1)

ETACS-
ECU

IG1
RELAY

FUSIBLE
LINK

41

FUSIBLE
LINK

40

FUSIBLE
LINK

39

Wire colour code
B : Black LG : Light green G : Green L : Blue W : White Y : Yellow SB : Sky blue
BR : Brown O : Orange GR : Grey R : Red P : Pink V : Violet PU : Purple SI : Silver

AC612144

AC701453

Connectors: A-23X, A-24X, A-30X, A-32X

A-32X

A-23X

A-24X

AB

A-30X

AC701094

Connector: C-15 <LHD>

AH

C-15 (B)

AC701121

Connectors: C-15, C-127, C-128 <RHD>

AI

C-15 (B)

C-128

C-127 (BR)

AC701093

Connectors: C-52, C-53, C-127, C-128 <LHD>

C-52

C-53

C-127 (BR)

C-128

AM

AC701122 AM

Connectors: C-52, C-53 <RHD>

C-52

C-53

AC701240

AO

Connector: C-317 <LHD>

ETACS-ECU

AC701241

AP

Connector: C-317 <RHD>
ETACS-ECU

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-78

COMMENTS ON TROUBLE SYMPTOM
If the PTC heater does not work when the following
conditions are met, the PTC heater, PTC heater
relay, A/C-ECU, or wiring harness, connector(s) may
be defective.

• Blower knob: Other than OFF

• The engine is running.

• The engine coolant temperature is 77°C or lower.

• Temperature adjustment knob: MAX HOT

• During low-electric load conditions

PROBABLE CAUSES

• Malfunction of the PTC heater

• Malfunction of the PTC heater relay1

• Malfunction of the PTC heater relay2

• Malfunction of the PTC heater relay3

• Damaged wiring harness or connectors

• Malfunction of the A/C-ECU

DIAGNOSTIC PROCEDURE

STEP 1. M.U.T.-III diagnosis code
Check that the air conditioner has not set a diagnosis
code.

Q: Is the diagnosis code set?

YES :

Carry out the diagnosis code procedures.

Refer to .

NO :

Go to Step 2.

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-79

STEP 2. M.U.T.-III other system's diagnosis code
Check that the ETACS-ECU has not set a diagnosis
code.

Q: Is the diagnosis code set?

YES :

Carry out the diagnosis code procedures.

Refer to GROUP 54A, ETACS-ECU .

NO :

Go to Step 3.

STEP 3. Connector check: A-24X PTC heater
relay1 connector, A-32X PTC heater relay2
connector and A-23X PTC heater relay3
connector

Q: Is the check result normal?

YES :

Go to Step 4.

NO :

Repair the connector concerned.

STEP 4. Check the PTC heater relay1, 2 and 3.
Refer to .

Q: Is the check result normal?

YES :

Go to Step 5.

NO :

Replace the PTC heater relay1, 2 or 3.

STEP 5. Connector check: C-52 PTC heater
connector and C-15 A/C-ECU connector

Q: Is the check result normal?

YES :

Go to Step 6.

NO :

Repair the connector concerned.

STEP 6. Measure the voltage at C-52 PTC heater
connector.
(1) Disconnect the connector, and measure at the

wiring harness side.

(2) Ignition switch: ON
(3) Disconnect A/C-ECU connector C-15 and earth

terminal 6.

(4) Voltage between terminal 2 and body earth

OK: System voltage

Q: Is the check result normal?

YES :

Go to Step 13.

NO :

Go to Step 7.

STEP 7. Measure the voltage at A-24X PTC heater
relay1 connector.
(1) Remove the relay, and measure at the relay side.
(2) Voltage between terminal 2 and body earth

OK: System voltage

Q: Is the check result normal?

YES :

Go to Step 9.

NO :

Go to Step 8.

STEP 8. Check the wiring harness between A-24X
PTC heater relay1 connector terminal No. 2 and
fusible link (40) connector.
NOTE: Prior to the wiring harness inspection, check
glow control relay connector A-30X, and repair if nec-
essary.

• Check the power supply line for open circuit.

Q: Is the check result normal?

YES :

Intermittent malfunction (Refer to GROUP

00

− How to Use Troubleshooting/

Inspection Service Points - How to Cope
with Intermittent Malfunction ).

NO :

Repair the wiring harness.

STEP 9. Measure the voltage at A-24X PTC heater
relay1 connector.
(1) Remove the relay, and measure at the relay side.
(2) Turn the ignition switch to the "ON" earth position.
(3) Voltage between terminal 3 and body earth

OK: System voltage

Q: Is the check result normal?

YES :

Go to Step 11.

NO :

Go to Step 10.

STEP 10. Check the wiring harness between A-
24X PTC heater relay1 connector terminal No. 3
and C-317 ETACS-ECU connector terminal No. 5.
NOTE: Prior to the wiring harness inspection, check
intermediate connector C-128, and repair if neces-
sary.

• Check the power supply line for open circuit.

Q: Is the check result normal?

YES :

Intermittent malfunction (Refer to GROUP

00

− How to Use Troubleshooting/

Inspection Service Points - How to Cope
with Intermittent Malfunction ).

NO :

Repair the wiring harness.

STEP 11. Check the wiring harness wires
between C-52 PTC heater connector terminal No.
2 and A-24X PTC heater relay1 connector
terminal No. 4.

• Check the power supply line for open circuit.

Q: Is the check result normal?

YES :

Go to Step 12.

NO :

Repair the wiring harness.

TROUBLESHOOTING

HEATER, AIR CONDITIONER AND VENTILATION

55A-80

STEP 12. Check the wiring harness between A-
24X PTC heater relay1 connector terminal No. 1
and C-15 A/C-ECU connector terminal No. 6.
NOTE: Prior to the wiring harness inspection, check
intermediate connector C-127, and repair if neces-
sary.

• Check the power supply line for open circuit.

Q: Is the check result normal?

YES :

Intermittent malfunction (Refer to GROUP

00

− How to Use Troubleshooting/

Inspection Service Points - How to Cope
with Intermittent Malfunction ).

NO :

Repair the wiring harness.

STEP 13. Measure the voltage at C-52 PTC heater
connector.
(1) Disconnect the connector, and measure at the

wiring harness side.

(2) Ignition switch: ON
(3) Disconnect A/C-ECU connector C-15 and earth

terminal 7.

(4) Voltage between terminal 3 and body earth

OK: System voltage

Q: Is the check result normal?

YES :

Go to Step 20.

NO :

Go to Step 14.

STEP 14. Measure the voltage at A-32X PTC
heater relay2 connector.
(1) Remove the relay, and measure at the relay side.
(2) Voltage between terminal 4 and body earth

OK: System voltage

Q: Is the check result normal?

YES :

Go to Step 16.

NO :

Go to Step 15.

STEP 15. Check the wiring harness between A-
32X PTC heater relay2 connector terminal No. 4
and fusible link (39) connector.

• Check the power supply line for open circuit.

Q: Is the check result normal?

YES :

Intermittent malfunction (Refer to GROUP

00

− How to Use Troubleshooting/

Inspection Service Points - How to Cope
with Intermittent Malfunction ).

NO :

Repair the wiring harness.

STEP 16. Measure the voltage at A-32X PTC
heater relay2 connector.
(1) Remove the relay, and measure at the relay side.

(2) Turn the ignition switch to the "ON" earth position.
(3) Voltage between terminal 3 and body earth

OK: System voltage

Q: Is the check result normal?

YES :

Go to Step 18.

NO :

Go to Step 17.

STEP 17. Check the wiring harness between A-
32X PTC heater relay2 connector terminal No. 3
and C-317 ETACS-ECU connector terminal No. 5.
NOTE: Prior to the wiring harness inspection, check
intermediate connector C-128, and repair if neces-
sary.

• Check the power supply line for open circuit.

Q: Is the check result normal?

YES :

Intermittent malfunction (Refer to GROUP

00

− How to Use Troubleshooting/

Inspection Service Points - How to Cope
with Intermittent Malfunction ).

NO :

Repair the wiring harness.

STEP 18. Check the wiring harness wires
between C-52 PTC heater connector terminal No.
3 and A-32X PTC heater relay2 connector
terminal No. 2.

• Check the power supply line for open circuit.

Q: Is the check result normal?

YES :

Go to Step 19.

NO :

Repair the wiring harness.

STEP 19. Check the wiring harness between A-
32X PTC heater relay2 connector terminal No. 1
and C-15 A/C-ECU connector terminal No. 7.
NOTE: Prior to the wiring harness inspection, check
intermediate connector C-127, and repair if neces-
sary.

• Check the power supply line for open circuit.

Q: Is the check result normal?

YES :

Intermittent malfunction (Refer to GROUP

00

− How to Use Troubleshooting/

Inspection Service Points - How to Cope
with Intermittent Malfunction ).

NO :

Repair the wiring harness.

STEP 20. Measure the voltage at C-52 PTC heater
connector.
(1) Disconnect the connector, and measure at the

wiring harness side.

(2) Ignition switch: ON
(3) Disconnect A/C-ECU connector C-15 and earth

terminal 5.