I am always being asked where the defrost timer is located on a refrigerator. Unfortunately the location varies depending on the manufacturer and model. Some are located in the rear near the compressor. Others are behind the louvered kick-plate in the front. Some are in the fresh-food section near the cold control. To make finding them more challenging they are usually covered except for a hole that allows them to be manually advanced. On the refrigerator that I use the timer is in the fresh-food section beside the cold-control. The only indication is the hole that permits a large flat blade screwdriver to be used to advance the timer.
Fig 1 Typical Defrost Timer
In a typical defrost circuit 120 volts is passed to the timer from the cold-control when it calls for cooling. The voltage energizes a clock circuit. If the defrost timer is in the defrost position, voltage is sent to the defrost heater circuit. If the timer is not in defrost, voltage is passed to the compressor starting-circuit and fans.
Fig 2 Typical defrost circuit (defrost cycle)
Some defrost circuits power the clock with line-voltage (bypassing the cold-control). This arrangement initiates a defrost cycle at set intervals of time regardless of how often the compressor has run. In the circuit above the clock runs only when the cold-control is made so it initiates a defrost cycle based on accumulated compressor run-time. With the defrost timer in the defrost position current goes to the defrost heater. The thermostat in the circuit (also called a termination thermostat) opens to turn off the defrost heater when the temperature in the freezer reaches its design temperature. This is usually around 50 to 55 degrees. This keeps the freezer compartment from getting too hot before the defrost timer switches back to the compressor run position. If the thermostat fails in the open position no current can flow through the defrost circuit even though the defrost timer and defrost heater are good. In this case the evaporator will frost up and eventually the freezer and fresh-food compartment temperatures will rise. The same symptoms will occur if the clock in the defrost timer fails and never switches to a defrost cycle or if the defrost heater fails.
Fig 3 Typical defrost circuit (in compressor run position)
Normally the termination thermostat will turn off the defrost heater before the defrost timer times out and switches the defrost heater out of the circuit. When the timer times out the defrost timer opens the heater circuit and closes the contacts to send power to the compressor and fans. The defrost timer stays in this position until the accumulated time to switch back to defrost cycle.
i have a ftx22cr ge that shows snow
on the wall of freezer
we hardly never get below 32°F
timer never seen running
heater circuit ohms measurement never taken yet.
compresor running all times .the system looks
“wiling to cool” but performance is insufficient.
what would be the next step here
This is clearly a defrost problem OR a defective evaporator fan that isn’t circulating air. If possible turn fridge off and let evap thaw completely. There may be more water than drain pan can hold so be aware that the pan will likely have to be emptied a few times. If you can determine how to remove cover from evaporator, it will expedite melting. Once the evap is clear of ice start fridge to see if fan starts. The likely problem is a bad defrost timer, defrost heater element, or defective defrost termination thermostat. With the ice off the evap (and a good fan)…the unit will cool properly for a few days even if one of the above parts are defective.
i have a defrost problem that im gonna try to fix, but i don’t have a multimeter to check the parts. i have manually turned the timer to defrost cycle, but defrosting doesn’t occur. would this mean a bad thermostat or bad heater? i plan on replacing one part at a time to see what the problem is. which part would you replace first? thanks.
The defrost heater and its termination thermostat fail more often than the thermostat (cold control). The termination thermostat is a two wire device clipped to the evaporator which cuts off power to the heating element if the temperature rises to approximately 50 degrees F before the defrost timer times out. If the termination thermostat is defective, no power flows through defrost heating element. A termination thermostat is less costly than a heating element. Defective defrost heating elements sometimes have obvious physical damage (and sometimes not).
I have an HOOVER GS20X7D3 and the imported defrost heaters always toast. I live in Europe and we have 220 V. Could it be theat these heaters are only for 120 Volts?
Pollux,
Since all the many defrost heaters that I have replaced/tested were 120v, I have never encountered the question of whether the voltage-rating of a replacement defrost heating element was incorrect. If the “toasting” occurs as soon as power is applied to the heater, I would conclude that your suspicion could be correct. A defrost heating element has a fixed resistence so applying 220v to a 120v element would double the amperage (current) and lead to ‘toasting’.
i have a Maytag Fridge and to be honest i dont know what the model is bc it was here when i started renting the house and i dont have any paperwork on it but i believe i have a defrosting problem.
its a side-by-side fridge and the temp started rising inside the fridge the past couple of days i pulled off the covering for the evaperator and all that located in the freezer caked with ice. I am currently letting it defrost right now and i see the copper tubing that runs through the back of the fridge
what else should i look for OR have to check?
Wes,
Sounds very much like the automatic defrost system has failed. Depending on the age of the appliance, you may be dealing with a defrost timer (using a mechanical timer) or adaptive defrost (using electronic control board). Many side-by-side fridges have two defrost heater elements so that the ice does not form over the whole evaporator. since one element is able to melt some of the ice block. A visual inspection will determine which element has failed. If the block covers the whole evaporator from top to bottom, either the termination thermostat or control (timer or control board) has failed. Does the landlord have documentation for the fridge and what is his/her responsibility to pay for repairs under the lease?
Dear Sir;
I have a Whirlpool Fridge that a problem with the Freezer and Lower Fridge section Temp. Upon inspection, The Freezer does not defrost, The problem that a while ago a repair man changed the defrost timer and defrost thermostat.
I noticed that the Timer is not running, I also noticed that the timer is currently wired so it runs when the copressor is off (The oposite of what you mentioned). I’m worried that the repair man changed the wiring on the fridge and that is the problem now. Also since the fridge is warm, the cool control does not cause it to stop and it runs all the time without defrosting.
Are you aware of any defrost timers wired to that the timer motor runs only when the cool control switched the compressor off.
There is mo wiring diagram on the frdige.
Thanks
Hani,
I have never encountered a defrost timer wired to run with the compressor off unless it the type that runs continuously and initiates defrost based strictly on elapsed time rather than compressor run time. Most defrost timers have a four-wire female connector that ensures that the chassis wiring connects to the proper terminals of the defrost timer. Not all defrost timers have the same terminal configuration so it is possible to use a replacement part that is not correct for the Whirlpool wiring. This would be the first thing that I checked with the aid of the fridge schematic. The defrost timer clock should be running all the time or when the compressor is running depending on the circuit design.
I checked a little further. The Timer installed is the correct one, The wiring is correct as far as I cxan tell, The color codes on timer match the color codes on the connector.
The Timer does not move at all. If I manually move the timer to the start of a defrost cycle, a defrost cycle starts, copressor off, Heater on and lasts for about 25 minutes then the compressor starts again. As soon as the compressor is on the timer stops.
Does that ring a bell??
Hani
Fridgeman I have a fridgedaire model FRT21NRHW4 fridge does not get cold evaporator fan runs compressor does not run, it hums when calling for cooling the overload kicks in, i’ve changed start components with a 3 in one start kit, compressor still hums on start up is the compressor baad or where do I go from hear
It sounds as if the compressor could have internal damage. Have you checked windings with a VOM? Also if the supply voltage is 10% below the rated voltage of the compressor, the overload will trip, keeping the compressor from starting.
Hi Fridgeman. I have a Whirlpool EL87TRRRS01 all fridge. The unit is not getting cold enough. It goes down to 34F some times but soon thereafter will be at mid to high 40s. I have reviewed the blog and tried some of the solutions you offer. The unit does get cold and form frost on the evaporator with the cover off, and there is no frost build up normally on the avaporator, The heater is at 34 ohms and evaporator fan is fine, I replaced the defrost timer, which seems to be working properly, as well as the cold thermostat. The condensor is clean and gets hot, as does the compressor. I can’t see how the defrost thermostat can be the culprit as it should not be a factor once the defrost timer triggers the cold cyde again. I am stumped. Any suggestions would be appreciated. Thx, David
Hello! I have a kenmorre side by side and the defroster seems to run constantly. the faces of the door seal surface is always hot. I advanced the timer but that does not seem to help. Any ideas on what would cause this?
I appreciate any help anyone can give me with this problem.Thank You!
Some refrigerators have electric door seal heaters to keep down condensation. They can be turned off with a small switch located on the cold control housing that says ‘energy saving’. Some older models routed the condenser beneath the skin surrounding the door to provide heat. These types cannot be turned off.