Tip & How-To about Refrigerators

How to check a defrost timer

Directions for testing a refrigerator defrost timer.

Before you begin to test your defrost timer, make sure you disconnect the appliance's power supply. The easiest way to do this is to unplug the unit from the wall. Alternatively, you could trip the appropriate switch in the circuit breaker panel, or you could remove the appropriate fuse from your home's fuse box.

Consult with an appliance repair technician if you do not feel you have the skill or the ability to successfully complete this repair.

  1. Locate your defrost timer. It can be located behind the refrigerator's lower kickplate, in the refrigerator's control panel, or even behind the refrigerator on its back wall. Defrost timers almost always have four metallic terminals extending from the bottom. Once you have found your refrigerator's defrost timer, remove it for testing.

  2. Remove all the screws holding the timer and pull the timer carefully out of the refrigerator. Pull it out far enough so that you can disconnect its wires.Be sure to label the wires and note their location. Pull firmly on the wire's connectors to remove them. You may need to rock them back and forth a little to ease the motion.

  3. Use a multimeter to test the timer for continuity. Set your multimeter to the R X 1 scale. Place one of the meter's leads on the common terminal. It should be labeled "3" or "C". If none of the terminals are labeled, you can locate the common terminal by determining which terminal coincides with the white wire in the connector plug. With one multimeter lead (probe) touching the common terminal, touch the other lead to the other three remaining terminals, one at a time. Testing the first pair should produce a reading of zero, or near zero, denoting continuity. The second pair may also result in a reading of zero or near zero. Testing the third pair of terminals should produce a reading of infinity.

  4. Find your refrigerator's timer switch and turn it in a clockwise motion until it clicks. Use your multimeter and test the terminals again in the same manner as in the preceding paragraph. In this test, one of the pairs of terminals should produce a reading of continuity. At least one pair, but maybe two, should produce a reading of infinity. One important note to keep in mind is that a pair of terminals that demonstrated continuity in the first test should now demonstrate infinity. Likewise, a pair of terminals that demonstrated infinity in the first test should now demonstrate continuity.

  5. If the test you conduct with your defrost timer does not produce these results, then you should replace the timer.

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1 Answer

The unit I'm working on has a 1 month old 8145-20ex and now the unit wont go into defrost - The compressor and the evap do not stop and the heaters do not energize. I'm thinking the defrost termination limit switch is bad. What is the easist way to check?

Copy following links:
8145-20 is 240Volt defrost timer.
The defrost cycle will not begin. This implies that trippers are not in place, or trippers are worn out.... or limit switch is stuck ON or solenoid inside timer has gone bad.
Test across terminal N to X for 240Volt. Because voltage here will stop defrost cycle by activating solenoid inside timer, but continuous voltage will also stop next defrost cycle from beginning. Disconnect wire on terminal X and see if defrost cycle will begin at next tripper. If defrost begins, then limit switch is bad.

Aug 06, 2013 | Hardware & Accessories

1 Answer

my whirlpool ed5fgexss00 wont get cold

Look at rear wall inside the back of the freezer and see if a frost line is building on rear wall. I have a feeling your freezer is not defrosting properly and not sure exactly what number you model has but checking the defrost timer Click Here=> ED5FTGXKQ00 Controls is where I would begin.We will need to run a couple test to make sure your=> 2323198 Heating Element and Defrost Thermostat=> 2321799 Defrost Thermostat are working properly.Testing heating element is also shown on same page above.Try turning the defrost timer clockwise slowly until refrigerator compressor stops running. This will place the freezer in manual defrost. Then tell me if once you do this if freezer begins defrost. If yes then the defrost timer=> 482493 Defrost Timer is at fault. If stays in defrost simply turn again until compressor restarts again. After doing this I will want you to watch this how to replace defrost heater=> Here I know this may be a little confusing but defrosting manually will help you see which parts may be needed. I will be here to answer any questions you may have, Thanks, Sea Breeze

Jan 08, 2012 | Whirlpool 25.4 Cu. Ft. Side-by-Side...

1 Answer

ice forming on the back wall of refrigerator compartment It is a side by side...twenty years old

Hello there,

When you are experiencing ice build up in your refrigerator and a part of the refrigerator is not getting cold, either the fridge or freezer compartment. Then it means there is a problem with a part in the unit.

Investigate these three areas if frost and ice are forming in your freezer and your fridge is not cold enough, test Defrost Timer, Defrost Heater and the defrost thermostat when you detect where the problem is from, replace it.

Before you begin to test your defrost thermostat, defrost heater and defrost timer, make sure you disconnect the appliance's power supply.
Here are some tips for you to go through in order to solve the problem.
Defrost timer testing http://www.fixya.com/support/r10523722-test_defrost_timer Defrost timer replacement http://www.fixya.com/support/r10523742-replace_defrost_timer
Defrost thermostat testing http://www.fixya.com/support/r10513592-test_defrost_thermostat Defrost thermostat replacement http://www.fixya.com/support/r10513650-replace_defrost_thermostat
Defrost heater testing: http://www.fixya.com/support/r10523771-test_defrost_heater Defrost heater replacing: http://www.fixya.com/support/r10523754-replace_defrost_heater
All the best Elect_Comp

Sep 21, 2011 | Sub-Zero 695/O Side by Side Refrigerator

1 Answer

without doing the minimal setting test to see if a time clock works how do you test a time clock with defrost termination the x terminal

8145-20 is 240Volt defrost timer:

You are testing the 8145-20 timer.
The timer dial should rotate continuously. Trippers on dial rotate around. When they reach the trip switch, the timer starts the defrost cycle.
Terminal 3 has power during defrost cycle.
Terminal 4 has no power during defrost cycle.
With 240Volt timer, terminals 1 and 2 and N and X test for live power to ground at all times.

The limit switch is connected to terminal X and to terminal N.
During the defrost cycle, the limit switch measures the pressure or temperature.
When pressure or temperature reaches the set point, the limit switch closes the circuit and this trips the solenoid inside timer. The solenoid turns off the timer relay, and the defrost cycle ends.
At this point the timer turns off the defrost, and sends power to the refrigeration.
Terminal 3 has no power during refrigeration cycle. (The opposite of defrost cycle).
Terminal 4 has power during refrigeration cycle.
Test these terminals for power to ground. One or the other should have power at all times, but not both.

If timer will not enter defrost cycle, make sure the X-3596 trippers are not worn down.
Disconnect the wire to terminal X and see if defrost cycle will start.
Test terminals 3 and 4 again and see if removing wire from X caused a change.

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Sep 14, 2011 | Paragon 8145-20 Defrost Timer

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