The diagnosis of electrical faults on components and compressors has already been dealt with in previous articles. The following procedure may be carried out to quickly pinpoint the faulty component and to eliminate unnecessary dismantling. The electrical circuit is tested for continuity from the terminal board of the circuit. The typical electrical circuit in Figure 61 has been chosen for the test procedure.
Steps 1 and 2 of the test procedure can be disregarded if the refrigerator or freezer has an interior light. This will come on when the appliance door is opened, unless the light bulb itself is defective.
The procedure is as follows:
1. Test for continuity from points 1 to 2, which will test the whole circuit.
2. Test from point 3 to points 1 and 2 to reveal any earth fault.
3. Test from points 1 to 8, which eliminates half of the circuit.
4. If the fault is in section 1 to 8, test between points 1 and 5 to determine if the fault is due to a loose connection, a defective cable or a blown fuse.
5. Should the fault be located in section 5 to 8, then the thermostat must be considered inoperative because the interior light and door switch will be isolated when the door is closed.
6. If the fault is in the compressor half of the circuit, it should be located in a similar manner by dividing into sections until it has been finally determined.
When an ohmmeter is used to test for continuity, it should normally be set to read off the x 1 scale. If the total resistance of the circuit is in excess of 100 ohms, the x 10 scale will be required; reset to the x 1 scale when the faulty section is isolated to less than 100 ohms.
Figure 62 shows a typical refrigerator/freezer electrical circuit.