With Automatic Climate Control

TROUBLE DIAGNOSIS PROCEDURE FOR BLOWER MOTOR

INSPECTION FLOW:

SYMPTOM:
- Blower motor operation is malfunctioning.
- Blower motor operation is malfunctioning under out of starting fan speed control.

SYSTEM DESCRIPTION

Component parts
Fan speed control system components are:
1. Auto amp.
2. Fan control amp.
3. A/C LAN system (PBR built-in air mix door motor, mode door motor and intake door motor)
4. In-vehicle sensor
5. Ambient sensor
6. Sunload sensor
7. Intake sensor

System Operation

Automatic Mode
In the automatic mode, the blower motor speed is calculated by the automatic amplifier based on inputs from the PBR, in-vehicle sensor, sunload sensor, intake sensor and ambient sensor. The blower motor applied voltage ranges from approximately 5 volts (lowest speed) to 12 Volts (highest speed).

The control blower speed (in the range of 5 to 12 Volt), the automatic amplifier supplies a gate voltage to the fan control amplifier. Based on this voltage, the fan control amplifier controls the voltage supplied to the blower motor.

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 50° C (122° F), the blower will not operate for a short period of time (up to 126 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 126 seconds as described above. After this delay, the blower will operate at low speed until the engine coolant temperature rises above 55° C (131° F), at which time the blower speed will increase to the objective speed.

Start Up From Normal or "HOT SOAK" Condition (Automatic mode)
The blower will begin operation momentarily after the AUTO button is pushed. The blower speed will gradually rise to the objective speed over a time period of 3 seconds or less (actual time depends on the objective blower speed).

Blower 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 high sunload, the blower low speed is "normal" low speed (approx. 6 Volt). During low or no sunload conditions, the low speed will drop to "low" low speed (approx. 5 Volt).

Ambient
When the ambient temperature is in the "moderate" range [10 - 15° C (50 - 59° F)], the computed blower voltage will be compensated (reduced) by up to 3.5 Volt (depending on the blower speed). In the "extreme" ambient ranges [below 0° C (32° F) and above 20° C (68° F)] the computed objective blower voltage is not compensated at all. In the ambient temperature ranges between "moderate" and "extreme" [0 - 10° C (32 - 50° F) and 15 - 20° C (59 - 68° F)], the amount of compensation (for a given blower speed) varies depending on the ambient temperature.

Fan Speed Control Specification:

COMPONENT DESCRIPTION

Fan Control Amplifier
The fan control amplifier is located on the cooling unit. The fan control amp. receives a gate voltage from the auto amp. to steplessly maintain the blower fan motor voltage in the 5 to 12 Volt range (approx.).