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Blower Motor Circuit





HEATING / AIR CONDITIONING: AIR CONDITIONING SYSTEM: Blower Motor Circuit
- Blower Motor Circuit

DESCRIPTION





The blower motor sub-assembly (with fan) is operated by signals from the air conditioning amplifier assembly. The blower motor sub-assembly (with fan) speed signals are transmitted by changes in the duty ratio.

Duty Ratio:

The duty ratio is the ratio of the blower motor sub-assembly (with fan) OPEN time (T1) to the total of the blower motor sub-assembly (with fan) OPEN and LO time (T2).

The air conditioning amplifier assembly controls the blower motor sub-assembly (with fan) speed.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. PERFORM ACTIVE TEST USING TECHSTREAM (BLOWER MOTOR SUB-ASSEMBLY)

(a) Select the Active Test, use the Techstream to generate a control command, and then check that the blower motor operates.

Air Conditioner





Result





C -- CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER - BLOWER MOTOR)

B -- CHECK HARNESS AND CONNECTOR (BLOWER MOTOR - BODY GROUND)

A -- PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE Symptom Related Diagnostic Procedures

2. CHECK HARNESS AND CONNECTOR (BLOWER MOTOR - BODY GROUND)





(a) Disconnect the A29 motor connector.

(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.

3. CHECK HARNESS AND CONNECTOR (BLOWER MOTOR - BATTERY)





(a) Disconnect the A29 motor connector.

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

Standard Voltage:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

4. CHECK BLOWER MOTOR SUB-ASSEMBLY (SI VOLTAGE)





(a) Disconnect the E36 amplifier connector.

(b) Reconnect the A29 motor connector.

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

Standard Voltage:





NG -- REPLACE BLOWER MOTOR SUB-ASSEMBLY Disassembly
OK -- Continue to next step.

5. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER - BLOWER MOTOR)





(a) Disconnect the E36 amplifier connector.

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

Standard Voltage:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY Removal

6. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER - BLOWER MOTOR)





(a) Disconnect the E36 amplifier connector.

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

Standard Voltage:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

7. CHECK AIR CONDITIONING AMPLIFIER ASSEMBLY (BLW SIGNAL)

(a) Remove the air conditioning amplifier assembly with its connectors still connected Removal.





(b) Using an oscilloscope, check the waveform.

Measurement Condition





OK:

Waveform is as shown in the illustration.

HINT
Waveform varies with the blower level.

NG -- REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY Removal

OK -- REPLACE BLOWER MOTOR SUB-ASSEMBLY Disassembly