Domestic Fridge /Freezer /Refrigerator  
DEFROST TIMER 6HR RUN / 30MIN DEFROST 220V

This means that the timer can ONLY operate on 220 volt power
this defrost timer switches the Defrost heater on Four times in Twenty Four hours . During  these intervals , the Compressor normally switches off and the Defrost heaters (sometimes) come on ( depending on the Ice Sensor / Switch)
The defrosting time is for 30 minutes. and then the cycle will resume

Defrost timer

Testing a Fridge /Freezer / Refrigerator Defrost Timer

The defrost timer helps to regulate the temperature in your Domestic Refrigerator and freezer by preventing ice build-up.

There is basically three things that can go wrong with a Fridge /Freezer / Refrigerator defrost timer

• The motor gears can wear out and not turn the timer

• The Timer motor itself can fail

• The timer Contact points can fail to either permanently open on close, or fail to open or close

• The heat fuse inside the Fridge /Freezer / Refrigerator can fail and prevent the timer motor from doing its duty. (See next to the Defrost heaters there could be a cold switch (Ice sensor) with a combination thermal Fuse / heat fuse )

To test a refrigerator's defrost timer.

The first thing you will have to do is to unplug the Domestic Fridge / Refrigerator from the wall socket outlet.

Do Not work on Domestic Fridge /Freezer / Refrigerator while it has power

Defrost Timer

Find the defrost timer. Depending on the make and model of your Fridge /Freezer / Refrigerator it may be found in one of the following areas:

• Behind the front grill in the freezer

• Behind the cover plate in the freezer

• Behind the freezer near the compressor

• Inside the temperature control console

Once you locate the defrost timer, look on the timer and find the advance screw. Turn it clockwise until you hear it click. Turn the power back on to the refrigerator. If the refrigerator was stuck in cool mode previously, this will advance it into defrost mode. Wait for about 30 to 40 minutes and then check it again to see if it advances back into the cooling mode. You will know when it begins cooling again, as the compressor will turn on.

If after 30 to 40 minutes you discover that the defrost timer is not advancing, then turn the power off to the refrigerator and remove the timer. The plug that connects to the timer can only be connected one way, so it's not important to draw a wiring schematic for this job.

If the timer did advance as it was designed to do, then you will now have to test the timer electronically. With the power off to the refrigerator, remove the defrost timer.

Take the timer to your workbench (Test the Timers Relay connections)

Set your multi-tester to read ohms. . If you look at the defrost timer, there should be four terminals. Find the terminal that is labeled "C" or "3." If the timer is not labeled, look at the connector plug to determine which terminal gets connected to the white wire; that is the common terminal.

Touch one of your tester's probes to the common terminal. Then, touch the other probe to each of the remaining terminals on the timer. As you touch the other terminals, one or two of the terminals (depending on the timer's current setting) should read "zero" and the remaining one or two should read "infinity."

Turn the advance screw again until you hear the click and then retest the terminals. This time, the results should be reversed. The terminal(s) that read "zero" earlier should now read "infinity" and the other(s) should now read "zero." It the timer does not pass this test, then it should be replaced.

If it does operate correctly, then return it to its position in the refrigerator.

The problem with your refrigerator may be caused by another issue like a faulty defrost heater, thermostat, Heat Fuse / Thermal fuse or even Faulty wiring

See basic / elementary Domestic Fridge /Freezer / Refrigerator wiring diagram with Defrost timer terminal numbering

Here is a diagram of the old type on unmarked Defrost timer