Blower Motor Circuit

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

DESCRIPTION





The blower motor is operated by signals from the air conditioning amplifier assembly. The blower motor speed signals are transmitted by changes in the duty ratio.

Duty Ratio:

The duty ratio is the ratio of the blower motor OPEN time (T1) to the total of the blower motor OPEN and LO time (T2).

The air conditioning amplifier assembly controls the blower motor speed.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. PERFORM ACTIVE TEST USING TECHSTREAM (FRONT BLOWER MOTOR)

(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 Problem Symptoms Table

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 FRONT BLOWER MOTOR (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 FRONT BLOWER MOTOR Removal
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 FRONT BLOWER MOTOR Removal