If it's a self-defrosting freezer, look at these parts..........the defrost timer, thermostat, or heater. Probably one of those.
Defrost Timer
A mechanical defrost timer controls the defrost cycle of the appliance. In older models, the timer runs continuously and roughly every six hours, shuts off power to the cooling system and sends power to the defrost heater. In newer models the timer advances only when the compressor or defrost cycle is running - an improvement for efficiency. As the timer advances, power to the heating element shuts off and power is restored to the cooling system. If the timer does not advance, the appliance will be stuck either in defrost or refrigerate mode, resulting in, respectively, no cooling or frost build-up.
The defrost timer is usually found behind the front grill of the freezer. It may also be found behind a cover plate inside the freezer, in the temperature control console, or behind the freezer near the compressor.
To test whether the defrost timer is simply failing to advance, locate the advance screw and turn it clockwise until you hear it click. This advances it to the next mode. If it was cooling before, it is now in defrost mode. Simply wait about 35 minutes and check whether it has left defrost mode and has resumed cooling (listen for the compressor). If it does not advance, the timer motor is probably bad and the entire timer needs to be replaced. If it advances as it should, then you can follow the steps below to test the switch electrically.
The timer is usually held in place with one or more screws. Remove the screws and gently pull the timer out far enough to disconnect the wiring connector. The connector can be removed by firmly pulling and rocking it left and right. It is not necessary to note the position of the wires because the connector plug is keyed so that it can be replaced in only one way.
Defrost thermostat
Some defrost systems use a thermostat (a bi-metal switch) to prevent the defrost heater from overheating. The switch is normally closed. During a defrost cycle, the defrost heater causes the metal alloy in the switch to warm and as it does it curls back and breaks the circuit. As the metal cools, it makes a circuit again and the defrost heater starts heating again (as long as the defrost timer is in the defrost cycle). A defective thermostat can prevent the defrost heater from coming on or allow it to overheat which could result in heat damage or fire.
The defrost thermostat is located near the defrost heater and is wired in series. It is usually located at the back of a side by side freezer or under the floor of a top freezer. It will be necessary to remove obstructions such as the contents of the freezer, freezer shelves, icemaker and the inside rear or bottom panel of the freezer.
The panel may be held in place by retainer clips or screws. Remove the screws or depress the retainer clips with a small screwdriver. On some older top freezers it is necessary to remove the plastic molding to access the freezer floor. Removal of that molding can be tricky -never force it. If you decide to remove it, you do so at your own risk - it is prone to breaking. Try warming it first with a warm, wet towel.
The thermostat is connected by two wires. The wires are connected with slip on connectors or a wiring harness. Firmly pull the connectors or harness off of the terminals (do not pull on the wire). You may need to use a pair of needle-nose pliers to remove the connectors. Inspect the connectors and the terminals for corrosion. If the connectors are corroded they should be replaced.
Test the thermostat for continuity using a multitester. Set the multitester to the ohms setting X1. Place a probe on each terminal. The multitester should display a reading of zero when the thermostat is cold and a reading of infinity when it is warm (40 to 90 degrees F depending on the model). If the thermostat does not pass this test it should be replaced.
Defrost Heater
The defrost heater is located at the back of the freezer. It may be necessary to remove obstructions such as the contents of the freezer, freezer shelves, ice maker and the rear or bottom inside panel of the freezer.
The rear panel may be held in place by retainer clips or screws. Remove the screws or depress the retainer clips with a small screwdriver.
There are three primary types of defrost heater elements; exposed metal rod, metal rod covered with aluminum tape or a wire coil inside a glass tube. All three elements are tested in the same way.
The heater is connected by two wires.Label the wires and connections so that you can properly reconnect them later. The wires are connected with slip on connectors. Firmly pull the connectors off of the terminals (do not pull on the wire itself). You may need to use a pair of needle-nose pliers to remove the connectors. Inspect the connectors and the terminals for corrosion. If either is corroded they should be cleaned or replaced.
Test the heating element for continuity using a multitester. Set the multitester to the ohms setting X1. Place a probe on each terminal. The multitester should display a reading somewhere between zero and infinity. If the reading is not between those two extremes the heating element should be replaced.
Facebook
Twitter