Blower Motor: Description and Operation

BLOWER MOTOR CONTROL SYSTEM


System Description


SYSTEM DESCRIPTION

Component Parts

Blower speed control system components are:
- A/C auto amp.
- A/C and AV switch assembly
- Variable blower control
- Front blower motor relay
- Front blower motor
- In-vehicle sensor
- Ambient sensor
- Optical sensor
- Intake sensor

System Operation






Automatic Mode
In the automatic mode, the blower motor speed is calculated by the A/C auto amp. and variable blower control based on input from the in-vehicle sensor, optical sensor, intake sensor and ambient sensor, and potentio temperature control (PTC).
When the air flow is increased, the blower motor speed is adjusted gradually 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 Blower 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 at blower speed 1 for a short period of time (up to 210 seconds). The exact start delay time varies depending on the ambient and engine coolant temperatures.
In the most extreme case (very low ambient temperature) the blower starting delay will be 210 seconds as described above. After the coolant temperature reaches 50�C (122�F), or the 210 seconds has elapsed, the blower speed will increase to the objective blower speed.
Start up from usual operating or hot soak condition (Automatic mode).
The blower will begin operation momentarily after the AUTO switch 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 speed will vary depending on the sunload. During conditions of low or no sunload, the blower operates at low speed. During high sunload conditions, the A/C auto amp. causes the blower speed to increase.

Blower Speed Control Specification

COMPONENT DESCRIPTION

Variable Blower Control





The variable blower control is located on the cooling unit. The variable blower control receives a gate voltage from the A/C auto amp. to steplessly maintain the blower motor voltage in the 0 to 5 volt range (approx.).