Fisher & Paykel 790 Active Smart, Service Manual

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6 ELECTRONICS SECTION
6.1 Overview Function Description
The electronic system consists of several parts:
Power/control module, display module, compressor, defrost heater, ambient heater, provision compartment
fan, freezer compartment fan, light, temperature sensors and door sensors.
The purpose of the power/control module is to turn on the compressor, which cools the evaporator, then to
use the fans to efficiently cool the compartments. Both fans turn on with the compressor. The freezer
compartment (FC) fan is kept at a constant speed while the provision compartment (PC) fan is regulated to
provide the balanced cooling for both compartments. The function of the microprocessor in the
power/control module is to provide independence of both compartments to their set temperatures, although
the environment of one compartment effects the other as they are linked by the ducts as can seen by the
diagrams showing internal air flow of the cabinet (diagrams 5.1A and 5.1B).
6.1.1 Control & Peripheral Functions
The control system consists of the power/control module located in the unit compartment of the refrigerator,
the slave display module located in the back of the refrigerator compartment and various sensors and
actuators controlled by the power module. The function and brief description of each of these units is
defined below.
6.1.2 Power/Control Module
This module is the electronic brain and control centre of the refrigerator. It contains a microprocessor,
support circuitry and switching devices. The power/control module controls the Provision Compartment (PC)
and Freezer Compartment (FC) temperatures by sensing the temperature and door state and operating the
compressor and fans accordingly. This module also houses the alarm beeper.
The power/control module collects information on the refrigerator operation. Faults and diagnostic
information is stored in its memory. They include the temperature setting, the history of FC and PC
temperatures (approx 18 hours), defrost history (the last 12 defrosts) and fault history. This will help the
service technician find and remedy the cause of failure. All this memory will be retained even when the
fridge is disconnected from mains power supply.
The beeper is used to signal prolonged door opening and other fault conditions:
1. If the door is left open longer than 90 seconds, the alarm will sound. This will repeat every 30 seconds
until the door is closed.
2. If the doors are left open longer than 5 minutes, the alarm will sound continuously and the PC light will
turn off. The alarm will stop with the closing of the door.
3. All electronic faults, when detected, will sound the alarm and the L.E.D.’s on the display module will flash
indicating the fault code. The pressing of any button will cancel the alarm but the fault code will remain
until the cabinet has been serviced.