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Operation and Function.
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Blower Speed Control
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| 1. |
Blower speed control function
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By varying the amount of current that passes through the blower motor the blower speed can be regulated. There are 2 methods: resistor type and transistor type.
| (1) |
Resistor type
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This adjusts the amount of current using a number of (blower) resistors connected in series. By operating the blower speed selector switch, the resistance value in the circuit is changed, which varies the amount of current flow.
For example; when placing the selector switch in the "LO" position, the current passes through both the resistors therefore, current flowing through the blower motor is reduced and the blower speed is low. Placing the selector switch in the "3" position, the current passes through only one resistor. Placing the selector switch in the "HI" position bypasses all the resistors therefore, the current only flows through the blower motor and the blower speed is greatest. |
| (2) |
Transistor type
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| This adjusts the amount of current using a power transistor. The transistor type can control the blower speed at an increased number of levels (or steps) when compared to the resistor type, so it is mainly used for automatic A/C systems. |
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