Lexus IS250 · Service Manual HEATER & AIR CONDITIONING SYSTEM

Blower Motor Circuit

Circuit diagnosis

DESCRIPTION

E107334E02
The blower motor is operated by signals from the A/C amplifier. The blower motor speed is controlled using various duty ratios.
Duty Ratio:
  1. The duty ratio is the ratio of the blower motor ON time (A) to the total of the blower motor ON and OFF time (A + B).
  2. The blower motor controller controls the blower motor speed.

WIRING DIAGRAM

E116881E03

INSPECTION PROCEDURE


1. PERFORM ACTIVE TEST BY INTELLIGENT TESTER

  1. Connect the intelligent tester to the DLC3.

  1. Turn the engine switch on (IG) and turn the intelligent tester main switch on.

  1. Select the item below in the Active Test and then check that the relay operates.

Active Test / Air Conditioner: 
Item
 Test Details / Display (Range)
 Diagnostic Note
Blower Motor
(Blower Motor)
 Blower motor / Min.: Level 01, Max.: Level 31
 -

Result:
Result
 Proceed to
OK
 A
NG (blower motor does not operate)
 B
NG (blower motor operates but does not change speed)
 C



B
Go to step 2

C
Go to step 6
A

PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE

2. INSPECT FUSE
E116895E02

  1. Remove the HEATER fuse from the engine room R/B and J/B No. 1.

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

    Standard resistance:
    Tester Item
    		 Condition
    		 Specified Condition
    HEATER fuse
    		 Always
    		 Below 1 Ω



NG
REPLACE FUSE (HEATER)
OK


3. CHECK WIRE HARNESS (BLOWER MOTOR - BODY GROUND)

  1. I041124E11
    Disconnect the blower motor connector.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    A34-1 (GND) - Body ground
    		 Always
    		 Below 1 Ω



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


4. CHECK WIRE HARNESS (BLOWER MOTOR - BATTERY)

  1. I041124E12
    Disconnect the blower motor connector.

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

    Standard voltage:
    Tester Connection
    		 Condition
    		 Specified Condition
    A34-3 (+B) - Body ground
    		 Always
    		 10 to 14 V



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


5. INSPECT BLOWER MOTOR

  1. E107336E10
    Disconnect the A/C amplifier connector.

  1. Connect the blower motor connector.

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

    Standard voltage:
    Tester Connection
    		 Condition
    		 Specified Condition
    A34-2 (SI) - Body ground
    		 Engine switch on (IG)
    		 4.5 to 5.5 V



NG
REPLACE BLOWER MOTOR
OK


6. CHECK WIRE HARNESS (A/C AMPLIFIER - BODY GROUND)

  1. E107331E09
    Disconnect the A/C amplifier connector.

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

    Standard voltage:
    Tester Connection
    		 Condition
    		 Specified Condition
    J58-11 (BLW) - Body ground
    		 Engine switch on (IG)
    		 4.5 to 5.5 V



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


7. INSPECT AIR CONDITIONING AMPLIFIER

  1. E107542E03
    Remove the A/C amplifier with its connectors still connected.

  1. Turn the engine switch on (IG) .

  1. Turn the blower switch ON (Lo).

  1. Measure the waveform between terminal J58-11 (BLW) of the A/C amplifier and body ground.

    OK:
    Waveform is as shown in the illustration.

    HINT:
    Waveform varies with the blower level.

Item
 Contents
Tool setting
 1 V/DIV., 500 μs/DIV.
Vehicle condition
 Engine switch on (IG)
Blower switch ON (Lo)


NG
REPLACE AIR CONDITIONING AMPLIFIER
OK

REPLACE BLOWER MOTOR


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