5303918568 Frigidaire Defrost Thermostat is a temperature-actuated safety switch used in frost‑free refrigerators and freezers to monitor evaporator temperature and control the defrost heater circuit. It is a passive electromechanical component-typically a thermostat or thermal cutoff device-designed to change state at a specified temperature range so that the defrost heater is allowed to run only when the evaporator has reached the appropriate temperature for safe and effective defrosting.
Inside the appliance the defrost thermostat is mounted in close thermal contact with the evaporator coil or secured by a clip on the evaporator assembly; it interfaces directly with the defrost heater and the control system (mechanical timer or electronic control board). its primary role is to prevent the heater from running when the evaporator is still cold, and to terminate the defrost cycle once the frost has been melted, providing both functional control of the defrost cycle and protection against overheating. The device therefore affects refrigeration system performance, ice accumulation on the evaporator, and can indirectly influence compressor runtime and system efficiency when it fails or operates out of specification.
In this article you will find a technical overview of the 5303918568 Frigidaire defrost thermostat including its intended function and typical operating behavior, guidance on model compatibility and identification, common failure symptoms to watch for, diagnostic checks a technician can perform (continuity and temperature‑response methods), and practical replacement considerations such as mounting, electrical ratings, and safety precautions. The focus is on clear, service‑oriented information that supports accurate troubleshooting and informed replacement decisions.
table of Contents
- Function and Role of the Defrost Thermostat in Refrigerator Defrost Control Systems
- How the 5303918568 Frigidaire Defrost Thermostat Operates Within the Defrost Circuit and temperature-Sensing Network
- Common Failure Symptoms and Diagnostic Indicators of a Faulty Defrost Thermostat
- Replacement Considerations, Model Compatibility, and Installation Procedure for the Defrost Thermostat
- Q&A
- in Retrospect
Function and Role of the Defrost Thermostat in Refrigerator Defrost Control Systems
The defrost thermostat monitors evaporator temperature and provides a safety interlock for the defrost heater circuit. The 5303918568 Frigidaire Defrost Thermostat is a snap-action bimetal device that is electrically closed at low coil temperatures and opens once the evaporator warms past its cutout threshold. In an automatic defrost cycle the refrigerator’s timer or control board will only energize the heater if the thermostat closes, so the part’s switching behavior directly controls whether frost is removed. A failed thermostat that remains open prevents the heater from running and causes frost buildup; a thermostat stuck closed allows repeated or extended heater operation until the timer or a thermal fuse interrupts the cycle.
Technicians test the device by measuring continuity at representative temperatures and by confirming proper mounting on the evaporator coil so it senses metal temperature rather than air. Typical service checks include verifying continuity with a multimeter after forcing the sensor cold (using ice or exposure to cold air) and confirming that the circuit opens after warming. Compatibility considerations include terminal type (usually two spade terminals), clamp or bracket mounting, and matching the thermostat’s cut-in/cut-out temperature range to the appliance control; replacing with an incorrect temperature rating can either prevent defrosting or allow unneeded heater operation.
- Common failure symptoms: persistent frost/ice buildup (open thermostat) or frequent defrost cycles/overheating (stuck closed).
- Typical physical interface: two rapid-disconnect spade terminals and a clamp-on sensor housing.
- Service steps: inspect mounting, measure cold continuity, warm sensor to confirm open circuit, replace if readings do not change.
| Item | Description |
|---|---|
| Part number | 5303918568 |
| Function | Closes at low evaporator temperature to enable defrost heater; opens when coil reaches cutout temperature |
| Type | Bimetal/snap-action thermostat; two-terminal switch |
| Typical behavior | Continuity at cold temperatures; opens as coil warms (exact thresholds vary by design) |
How the 5303918568 Frigidaire Defrost Thermostat Operates Within the Defrost Circuit and Temperature-Sensing Network
The 5303918568 Frigidaire Defrost Thermostat is a bimetal temperature-activated switch that sits in direct contact with the evaporator coil and is wired in series with the defrost heater and the defrost control (timer or control board). While the control initiates a defrost cycle, the thermostat provides local, temperature-dependent permission for heater current: it remains closed at low evaporator temperatures so the heater can operate, then opens when the sensed temperature rises past its designed setpoint to interrupt current and prevent overheating of the evaporator and surrounding components. Its physical mounting (clip or probe) and the electrical terminal style determine direct interchangeability with specific Frigidaire models,so replacement requires matching the mechanical fit and terminal configuration along with the part number.
In practical service terms the thermostat protects the defrost heater and limits unnecessary run time, and it also acts as a primary diagnostic point when defrost problems occur. for example, if a refrigerator does not defrost despite the control calling for a cycle, a technician should verify voltage at the heater and then test the thermostat for continuity at a cold evaporator-no continuity when the evaporator is cold indicates a failed-open device. Conversely, a thermostat that remains closed regardless of temperature will allow the heater to run until the control stops it, which can cause premature melting of frost and water overflow. Common symptoms and checks include:
- Excessive frost buildup on evaporator - check for failed-open thermostat or absent heater operation.
- Continuous water leaking after defrost - possible failed-closed thermostat allowing extended heater operation.
- No heater operation during an active defrost cycle – verify line voltage to heater and continuity across the thermostat when cold.
| Item | Description |
|---|---|
| Switch type | Bimetal temperature switch, typically closed at low evaporator temperature and opens when warmed. |
| Circuit role | Wired in series with the defrost heater to interrupt current when setpoint is reached. |
| service test | Measure continuity with evaporator cold; verify opens as temperature rises; confirm heater voltage during defrost cycle. |
Common Failure Symptoms and Diagnostic Indicators of a Faulty Defrost Thermostat
The 5303918568 Frigidaire Defrost Thermostat is a temperature-actuated switch mounted to the evaporator coil that completes the circuit to the defrost heater only when the coil temperature drops below a specified threshold. In normal operation the thermostat is closed when the evaporator is cold, allowing the timed defrost heater to receive current during a defrost interval; it opens as the coil warms to terminate the heater.A thermostat that sticks open prevents the heater from energizing and allows excessive ice build-up on the evaporator, while a thermostat that is shorted closed can allow prolonged heater operation, creating water intrusion or premature heater failure. Technicians should consider compatibility and mounting orientation when replacing this part, since improper seating on the evaporator tube alters thermal response and diagnostic readings.
- Visible heavy frost or thick rime on evaporator fins despite periodic defrost cycles.
- Warm refrigerator/freezer compartment with a running compressor and no cold airflow.
- Defrost heater never appears to energize (no current draw) or conversely runs continuously.
- intermittent cooling or long run times following defrost intervals,indicating incomplete or failed defrost.
- Localized ice pattern at the thermostat mounting point or corrosion/damage to the thermostat body.
Diagnostic checks include confirming continuity behavior across the thermostat at controlled temperatures and verifying that the control board/timer supplies voltage to the thermostat during a defrost cycle. With a multimeter, the thermostat should show continuity when chilled to the specified trip range and open when warmed; if continuity does not change with temperature the component is faulty. For isolation testing remove the thermostat from the evaporator and place it in an ice-water bath to confirm closure, and measure line voltage during a known defrost event to distinguish between a failed thermostat and a failed defrost control. For reference, typical electrical and mounting characteristics are summarized below - always verify exact trip temperatures and wiring against the appliance service manual before replacement.
| Item | Description |
|---|---|
| Expected electrical state | Closed (near 0 Ω) when below freezing; Open (OL) when above defrost threshold. |
| typical trip behavior | Closes at cold evaporator temperatures to allow heater energization; opens as coil temperature rises - verify OEM spec for exact °C/°F. |
| Mounting/compatibility | Clipped to evaporator tubing; 5303918568 fits specific Frigidaire models-match mounting style and wiring harness for correct thermal response. |
Replacement Considerations, Model Compatibility, and Installation Procedure for the Defrost Thermostat
5303918568 Frigidaire Defrost Thermostat is a bimetal defrost control designed to sense evaporator temperature and open the defrost heater circuit once the evaporator has warmed above its termination set point.In operation the device is typically closed at low evaporator temperatures (allowing the defrost heater to energize when the timer or control calls for defrost) and opens as the coil temperature rises, interrupting heater current to prevent overheating. Compatibility depends on mechanical mounting (clip or screw), lead length and terminal type, and the thermostat’s switching temperature; technicians should verify that the replacement matches the original part’s terminal style and temperature rating rather than relying only on the part number, since similar-looking thermostats can have different cut-in/cut-out temperatures or mounting hardware requirements.
Follow a controlled, documented procedure when replacing this thermostat: disconnect power, remove the evaporator cover, note the sensor orientation and clip location, disconnect wiring and remove the old sensor, and install the new unit in the identical position and orientation to preserve accurate temperature sensing. Use a continuity meter to confirm closed continuity at low temperature and an open state after warming (freezer-spray or a warm-air source can be used for bench testing). Practical checks after reassembly include initiating a manual defrost cycle (or advancing the electronic control) and verifying that the heater de-energizes when the evaporator warms to the thermostat’s termination range; if the heater stays powered or the thermostat never closes at low temperature,replace the device and re-check connections.
- Typical replacement checks: terminal type (quick-disconnect vs. screw),lead length,mounting clip orientation,and rated switching temperature.
| Item | Description |
|---|---|
| Part Number | 5303918568 (Frigidaire defrost thermostat OEM reference) |
| Switch Type | Bimetal thermal switch - closes at low temp, opens at defrost termination |
| Typical switching range | Closes at cold evaporator temperatures; opens as coil warms (model-dependent; commonly within a few °C/°F around the defrost termination point) |
| Termination/Leads | Quick-disconnect terminals; verify lead length and connector type before ordering |
Q&A
What is part 5303918568 and what does a defrost thermostat do?
Part 5303918568 is an OEM Frigidaire defrost thermostat (a temperature‑sensitive bimetal switch). It is clipped to the evaporator coil and is part of the automatic defrost circuit. When the evaporator is cold the thermostat remains closed so the defrost heater can be energized during a scheduled defrost. As the evaporator warms during defrost the thermostat opens at its cut‑out temperature to shut off the heater and prevent overheating.
Which Frigidaire models use this defrost thermostat?
This thermostat is used on a range of Frigidaire/Frigidaire Gallery/Kenmore units that share the same evaporator/defrost design. Model fit varies – always verify compatibility by checking your refrigerator model number against the part listing from Frigidaire or a reputable parts supplier before ordering. Do not rely on visual similarity alone.
What are common symptoms that 5303918568 has failed?
Typical failure signs include: excessive frost or ice build‑up on the evaporator or freezer walls, poor cooling or warm compartments, the compressor running continuously, or a defrost heater that never runs (if the thermostat fails open). If the thermostat fails stuck closed, the heater may be allowed to run longer than intended during defrost cycles, which can cause other problems – however the heater only runs when the defrost control calls for it.
How can I test the defrost thermostat safely?
Unplug the appliance frist. Locate and remove the back evaporator panel to access the thermostat (it’s usually clipped to the coil). Disconnect the two spade leads from the thermostat. Using a multimeter set to continuity or ohms: at freezer operating temperature the thermostat should show continuity (closed) – near 0 Ω. To confirm proper operation you can cool it (place in ice water or return it to the frozen evaporator) to verify it closes, then gently warm it with a hair dryer (or let the evaporator warm during a defrost) to see it open. If it does not change state appropriately, replace it. Always observe electrical safety and do not leave the heater energized while testing with a bypass jumper.
How do I replace 5303918568?
Unplug the refrigerator.Remove the evaporator cover/panel to expose the thermostat. Note or photograph the wiring, then disconnect the two spade connectors. Remove the clip or bracket that secures the thermostat to the evaporator tubing and install the new thermostat in the same position and orientation, securing it with the clip. Reconnect the spade terminals, reassemble the panel, and restore power. Because this is a line‑voltage component in the defrost circuit, follow safety precautions – if you’re not agreeable, hire a qualified technician.
What are the electrical/wiring details I should know?
The defrost thermostat is a simple two‑terminal, line‑rated temperature switch wired in series with the defrost heater. It is not polarity sensitive. You should not need to wire any additional components when replacing it – just transfer the two spade connectors. It is designed to switch the heater’s line voltage and should be replaced with an identical OEM or equivalent rated part.
can I temporarily bypass the thermostat to test the defrost heater?
Technically you can jumper the two thermostat terminals to test whether the defrost heater or timer works,but it is indeed not recommended for routine troubleshooting as bypassing prevents the thermostat from opening and can overheat or damage the evaporator and heater if left in that state. If you do jump the terminals for a quick test, do so only momentarily, monitor closely, and restore the thermostat immediately afterwards.
Where should I buy part 5303918568 and how do I confirm I have the correct part?
Buy from frigidaire/authorized parts dealers, reputable appliance parts stores, or trusted online retailers. Confirm compatibility by entering your refrigerator’s model number into the seller’s lookup tool or by cross‑referencing the Frigidaire parts diagram for your model. Keep your receipt and check the seller’s return policy in case the part is incorrect. If uncertain, provide your appliance model number to the supplier or a technician for verification.
In Retrospect
The 5303918568 Frigidaire defrost thermostat is a small but critical component in frost-free refrigerators and freezers, designed to sense evaporator temperature and control the defrost cycle so that frost accumulation is prevented, cooling efficiency is maintained, and compressor workload is minimized. Proper operation of this thermostat helps ensure consistent temperature performance, energy efficiency, and the longevity of the refrigeration system by engaging the defrost heater only when needed and protecting other components from damage due to excessive frost.
accurate diagnosis and timely replacement of a failing 5303918568 thermostat are important to restore normal defrost operation and avoid secondary issues such as uneven cooling, ice buildup, or premature component wear. Prior to replacement, confirm symptoms with appropriate tests or diagnostics and verify part compatibility; when in doubt, consult manufacturer guidance or a qualified technician. Replacing a defective thermostat with the correct part and following recommended installation procedures will help maintain appliance reliability and efficiency.
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