TPX21BRBEWW 12 Defrost Heater and Thermostat Kit – What Part Fixes Refrigerator Frost/Ice Build-Up

Understanding the Problem

What this kit is and why it matters: The TPX21BRBEWW 12 defrost heater and thermostat kit replaces the two components that melt frost from the evaporator coil during the defrost cycle: the defrost heater (an electrical heating element mounted near the evaporator) and the defrost thermostat/bi-metal (a temperature-sensitive switch that prevents the heater from overheating). If either part fails, the evaporator can ice over, blocking airflow and causing the freezer to over-freeze or the fridge to run constantly. Diagnostic and repair steps: 1) Safety first: Unplug the refrigerator or turn off its circuit breaker before doing any work. Remove food and allow the freezer to warm slightly if access is difficult. 2) Confirm the symptom: Look for heavy frost/ice on the evaporator (usually behind the rear freezer panel), freezer that stays excessively cold, fridge that’s warm, or water leaking when the ice finally melts. 3) Access the evaporator: Empty the freezer compartment, remove shelves and bins, then remove the back evaporator cover panel (usually held by screws or clips) to expose the evaporator, heater, and thermostat. 4) Visual inspection: Look for obvious damage to the heater (broken coil, burn marks), disconnected wires, or a thermostat that’s cracked/melted or has corroded leads. 5) Continuity test – defrost heater: With the fridge still unplugged, disconnect the heater leads and use a multimeter set to continuity or low ohms. The heater should show continuity (a low resistance reading). An open circuit (infinite resistance) means the heater is bad. 6) Continuity/operation test – defrost thermostat: Remove the thermostat and test with a multimeter. Place the thermostat in ice water (or a freezer-safe bag of crushed ice) and test continuity. It should close (show continuity) when cold (near freezing temperatures). If it never closes or is intermittent, replace it. 7) Check the defrost cycle control: If both heater and thermostat test good, check that the control actually powers the heater during a defrost cycle. For mechanical timers, manually advance to defrost and check for 120/240 V (depending on model) at the heater terminals. For electronic boards, consult the wiring diagram and test for the same during a commanded defrost. No voltage to the heater could indicate a bad timer or control board rather than the heater/thermostat. 8) Replace parts: If heater or thermostat fail the tests, replace them with the TPX21BRBEWW 12 kit or an equivalent. Typical replacement steps below. 9) Reassemble and test: After replacement, restore power and force a defrost cycle (advance timer or use diagnostics) to verify the heater runs and ice melts. Monitor the fridge for normal cooling behavior over the next 24–48 hours. Basic step-by-step replacement (how to fix): 1) Unplug refrigerator. Remove food and empty freezer compartment. Remove screws and the evaporator cover panel. 2) Take pictures of wiring before disconnecting anything. Disconnect the heater and thermostat leads and remove any clips or mounting hardware holding them to the evaporator. 3) Install the new heater: route the new heater element along the evaporator in the same position as the old one and secure with the original clips or supplied fasteners. Do not stretch the heater wire; avoid contact with sharp edges. 4) Install the new thermostat: mount it where the old thermostat was clipped against the evaporator tube or bracket. Ensure good thermal contact and secure the wiring. 5) Reconnect wiring according to your photos or wiring diagram. Replace the evaporator cover, shelves, and bins. 6) Plug the refrigerator back in. Force a defrost (advance timer or use the fridge diagnostic mode). Confirm the heater warms (careful — don’t touch it while powered) and ends when the thermostat opens or the control ends the cycle. 7) Monitor cooling and check for residual frost over the next day. Safety note: Always disconnect power before testing or replacing parts. If you’re uncertain about working with mains voltage or accessing internal components, hire a qualified appliance technician.

Common Symptoms

Evaporator iced over, poor cooling in refrigerator compartment, freezer extremely cold or uneven, long run times, water pooling or dripping when ice melts.

Common Causes

• Open or burned defrost heater element
• Failed defrost thermostat (bi-metal) not closing when cold
• Defrost control/timer or electronic control board not initiating defrost (voltage never reaches heater)

Popular Parts That Fix This Problem

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Frequently Asked Questions