Blower Motor Circuit

TROUBLE DIAGNOSIS


Blower Motor Circuit

SYMPTOM: Blower motor operation is malfunctioning.

INSPECTION FLOW











SYSTEM DESCRIPTION

Component Parts

Fan speed control system components are:
- Unified meter and A/C amp.
- A/C LAN system (PBR built-in mode door motor, upper ventilator door motor, air mix door motor and intake door motor)
- In-vehicle sensor
- Ambient sensor
- Sunload sensor
- Intake sensor

System Operation






Automatic Mode
In the automatic mode, the blower motor speed is calculated by the unified meter and A/C amp. based on the input from the PBR, in-vehicle sensor, sunload sensor, intake sensor and ambient sensor.
When the air flow is increased, the duty ratio of the blower fan motor's drive signal is changed at 8%/sec. to prevent a sudden increase in air flow.
In addition to manual air flow control and the usual automatic air flow control, starting air flow control, low water temperature starting control and high passenger compartment temperature starting control are available.

Starting Fan Speed Control
Start up from COLD SOAK Condition (Automatic mode)
In a cold start up condition where the engine coolant temperature is below 56�C (133�F), the blower will not operate for a short period of time (up to 150 seconds). The exact start delay time varies depending on the ambient and engine coolant temperature.
In the most extreme case (very low ambient) the blower starting delay will be 150 seconds as described above. After this delay, the blower will operate at low speed until the engine coolant temperature rises above
56�C (133�F), and then the fan speed will increase to the objective speed.
Start up from usual or HOT SOAK Condition (Automatic mode)
The blower will begin operation momentarily after the AUTO switch is pressed. The fan speed will gradually rise to the objective speed over a time period of 3 seconds or less (actual time depends on the objective fan speed).

Fan Speed Compensation
Sunload
When the in-vehicle temperature and the set temperature are very close, the blower will be operating at low speed. The low speed will vary depending on the sunload. During conditions of low or no sunload, the fan speed is at duty ratio 25%. During high sunload conditions, the unified meter and A/C amp. raise the fan speed (duty ratio 49%).

Fan Speed Control Specification

COMPONENT DESCRIPTION

Brush-less Motor





The blower motor utilizes a brush-less motor with a rotating magnet.





Quietness is improved over previous motors where the brush was the point of contact and the coil rotated.

DIAGNOSIS PROCEDURE FOR BLOWER MOTOR





SYMPTOM: Blower motor operation is malfunctioning.
1.CHECK POWER SUPPLY FOR BLOWER MOTOR
1. Disconnect blower motor connector.
2. Turn ignition switch ON.





3. Check voltage between blower motor harness connector M91 terminal 1 and ground.

1 - Ground: Battery voltage

OK or NG
OK - GO TO 2.
NG - Check power supply circuit and 15A fuses [Nos. 10 and 11, located in the fuse block (J/B)]. Fuse Block - Junction Box (J/B).
- If fuses are OK, check harness for open circuit. Repair or replace if necessary.
- If fuses are NG, check harness for short circuit and replace fuse.
2.CHECK BLOWER MOTOR GROUND CIRCUIT
1. Turn ignition switch OFF.





2. Check continuity between blower motor harness connector M91 terminal 3 and ground.

3 - Ground: Continuity should exist.

OK or NG
OK - GO TO 3.
NG - Repair harness or connector.
3.CHECK CIRCUIT CONTINUITY BETWEEN BLOWER MOTOR AND UNIFIED METER AND A/C AMP.
1. Disconnect unified meter and A/C amp. connector.





2. Check continuity between blower motor harness connector M91 terminal 2 and unified meter and A/C amp. harness connector
M64 terminal 38.

2 - 38: Continuity should exist.

OK or NG
OK - GO TO 4.
NG - Repair harness or connector.
4.CHECK UNIFIED METER AND A/C AMP. OUTPUT SIGNAL
1. Reconnect blower motor connector and unified meter and A/C amp. connector.
2. Turn ignition switch ON.
3. Set MODE switch to VENT position.
4. Change fan speed from 1 to 7, and check duty ratios between blower motor harness connector and ground by using an oscilloscope.

NOTE:
Calculate the drive signal duty ratio as shown in the figure.





T2 = 1.6 ms





OK or NG
OK - Replace blower motor after confirming the fan air flow does not change.
NG - Replace unified meter and A/C amp.

COMPONENT INSPECTION

Blower Motor





Confirm smooth rotation of the blower motor.
- Ensure that there are no foreign particles inside the blower unit.