THERMO Control Amplifier
The thermo control amplifier disconnects the magnet clutch circuit to prevent the evaporator from becoming frosted when the temperature of the evaporator fin drops close to 3°C (37°F). When the limit temperature is reached, the thermistor (located on the evaporator fin) interrupts the base current of the amplifier. This deactivates the A/C relay, which in turn disconnects the magnet clutch circuit.