Circuit Description

How the Circuit Works

Blower Controls

Battery voltage is provided at all times to the blower control relay contacts through fuse 5 in the under-hood fuse/relay box.

With the ignition switch in ON (II), battery voltage is supplied to the blower control relay coil through fuse 10 (in the under-dash fuse/relay box). The blower control relay energizes and supplies battery voltage to the blower motor. The blower motors speed is controlled by increasing or decreasing resistance to ground through the blower motor resistors and the blower switch. The blower motors ground path is completed when the blower switch is turned to positions L, M, or M1. The ground path runs through one or more blower resistors. Each time you move the switch to a higher speed, another resistor is bypassed. This results in decreasing the resistance which increases voltage across the blower motor. Blower speed will increase accordingly. In the H position, all of the resistors are bypassed and the blower motor runs at full speed.

Compressor Controls
(USA: Fit, Fit Sport; Canada: LX, Sport)

Voltage is supplied at all times to the A/C compressor clutch relay contacts through fuse 11 (in the under-hood fuse/relay box). With the ignition switch in ON (II), voltage is supplied to the A/C compressor clutch relay coil through fuse 10 (in the under-dash fuse/relay box).

When the blower switch is in any position except OFF and the A/C switch is pressed or the mode control switch is in position HEAT/DEF (X) or DEF (X), the ECM/PCM receives an A/C request signal through the A/C pressure switch. The A/C ON indicator will turn ON and the ECM/PCM will ground the A/C compressor clutch relay coil, providing battery voltage to the A/C compressor clutch.

When the mode control switch is in position HEAT/DEF (X) or DEF (X), the
Fresh/Recirculate slider should be moved to the Fresh (X) position.

Thermal Protector
(USA: Fit, Fit Sport; Canada: LX, Sport)

If the thermal protector, located on the A/C compressor, senses high temperature in the compressor, its switch will open, turning the compressor off. Once the compressor cools, the switch will close and the compressor will begin running again.

A/C Pressure Switch
(USA: Fit, Fit Sport; Canada: LX, Sport)

The A/C pressure switch is located in the condenser outlet line where refrigerant is in a high temperature/high pressure liquid state. The switch will sense abnormally high or low pressure and open the circuit. This removes the A/C request signal form the ECM/PCM, disengaging the compressor clutch.

Evaporator Temperature Sensor (USA: Fit, Fit Sport; Canada: LX, Sport)

The evaporator temperature sensor is located in the evaporator housing. If the temperature at the evaporator gets to cold, the evaporator temperature sensor sends a signal to the ECM/PCM to turn of the A/C compressor clutch. This prevents condensation from freezing on the evaporator fins and blocking air delivery into the passenger compartment.