318578506 Frigidaire Oven High limit Thermostat is a temperature-limiting safety device used in Frigidaire ovens and ranges; it is a mechanical/electromechanical thermostat that senses excessive temperatures and interrupts the heating circuit when a preset threshold is exceeded. As a high-limit control, it differs from the oven temperature sensor or control thermostat in that its primary purpose is safety rather than regular temperature regulationand it is typically specified to open or trip at a defined over-temperature point to protect the appliance and surrounding cabinetry.
Inside the appliance system the high limit thermostat monitors temperature in a designated area-commonly near the bake element,burner manifold,or oven cavity-and interfaces with the heater supply,control board,and safety interlocks. When the sensed temperature exceeds the device’s setpoint the high-limit opens its contact(s) to remove power from heating components or provide a fault signal to the control module; when closed it permits normal heating cycles dictated by the main control. Its operation is therefore integral to the thermal protection strategy and it interacts electrically and mechanically with wiring harnesses, relays/contactorsand other temperature-sensing devices in the oven.
In this article readers will find a technical description of the component’s function and operating principles, guidance on verifying compatibility with specific Frigidaire models, common failure symptoms (such as loss of heat, continuous overheatingor tripped safety circuits), step-by-step troubleshooting methods including visual inspection and multimeter continuity checksand practical replacement considerations like mounting orientation, connector typeand matching temperature ratings. Practical safety precautions and diagnostic steps appropriate for technicians, engineersand experienced appliance owners are included to support accurate diagnosis and safe replacement.
Table of contents
- Function and Role of the Oven High-Limit Thermostat in Frigidaire Electric Ranges
- how the 318578506 Frigidaire Oven High Limit Thermostat Operates Within the Control and Safety Circuits
- Common Failure Symptoms and Diagnostic Indicators of High-Limit Thermostat Faults
- Compatibility, Replacement Procedures, Installation Best Practices and Post-Installation Troubleshooting
- Q&A
- In conclusion
Function and Role of the Oven high-Limit Thermostat in Frigidaire Electric Ranges
The 318578506 Frigidaire Oven High limit Thermostat is a mechanical safety cutoff mounted in the oven cavity or chassis that interrupts the heating circuit when internal temperature exceeds a manufacturer-set threshold. It is normally a normally-closed device that opens at an over-temperature condition, preventing the bake and/or broil elements from continuing to draw power if the primary temperature control or control board fails. The component is not used for normal temperature regulation or user-setpoint control; instead it responds to sustained or runaway temperatures and holds the circuit open until the thermostat cools and resets or is replaced.
Technicians should match mounting location, terminal styleand electrical ratings when replacing this thermostat as improper fit or rating can leave the range without the required safety protection. Common diagnostic indications of a failed high-limit thermostat include an oven that will not heat (thermostat stuck open), an oven that continues to overheat despite control inputs (thermostat stuck closed), or intermittent heating behavior. For field testing, verify power is disconnected, then check for continuity at ambient temperature (expect closed) and loss of continuity when the sensing element is heated to its trip range under controlled conditions; consult the Frigidaire service manual for exact trip specification and replacement procedures.
- Primary function: safety cutoff that opens on sustained over-temperature to protect against runaway heating.
- Failure modes: stuck-open (no heat), stuck-closed (loss of over-temperature protection)or intermittent contact (erratic operation).
- Replacement considerations: match part number, mounting, terminal typeand electrical rating; verify compatibility with the specific Frigidaire model.
- Field test: continuity at ambient, open when heated to trip range (power removed before testing).
| Item | Description |
|---|---|
| Part | 318578506 Frigidaire Oven High Limit Thermostat |
| Function | Normally-closed safety thermostat that opens on over-temperature to interrupt heating circuit |
| Electrical/Mechanical Notes | Replace with same ratings and terminal style; consult service manual for trip temperature and wiring placement |
How the 318578506 Frigidaire Oven High Limit Thermostat Operates Within the Control and Safety Circuits
The 318578506 Frigidaire Oven High Limit Thermostat is a temperature-actuated safety interrupter installed in the oven’s control and safety circuits to prevent overheating. Functionally it is a normally closed device that opens its contacts when the sensed temperature exceeds its design setpoint, removing power from the bake/broil elements or from the control relay coil.In typical Frigidaire electrical schematics this high-limit is placed in series with the heater or the control board’s safety input so that an overtemperature condition forces a hard interrupt of the heating path rather than relying on software-driven shutdowns.
- Symptoms: no heat even though controls call for heat,or repeated shutdowns after reaching high temperature.
- Diagnostic checks: verify cold continuity across the thermostat terminals; inspect mounting and sensor exposure; confirm wiring continuity to the control board/element.
- Behavior note: some high-limits are self-resetting bimetal devices while others are one-time thermal fuses-check the part specification before replacing.
When the high-limit opens it typically prevents the control board from energizing the element relay, creating a clear series-interruption in schematic tracing; this prevents further temperature rise even if the control electronics fail. For practical troubleshooting, measure continuity with the oven cold and trace the circuit back to the control board or element; if the limit shows an open circuit at ambient temperature it should be replaced. Mechanical compatibility is straightforward for a direct-replacement part like this one-match terminal type and mounting location-and no field calibration is required as the trip setpoint is fixed by the thermostat element.
| Item | Description |
|---|---|
| Type | Normally closed temperature-actuated interrupt (bimetal or thermal fuse) |
| Primary function | Interrupt heating circuit on overtemperature to protect components and insulation |
| Service check | Continuity test when cold; replace if open at ambient temperature |
Common Failure symptoms and Diagnostic Indicators of High-Limit Thermostat Faults
The 318578506 Frigidaire Oven High Limit Thermostat is a safety switch mounted near the oven cavity or heating element that protects the appliance from sustained over-temperature conditions by interrupting power to the heating circuit. functionally it behaves as a thermally actuated, normally closed switch that opens at a preset limit to remove element or control-board power; in many Frigidaire ranges it is wired in series with the bake/broil relays so a failed-open device results in no heat, while a failed-closed device can allow unsafe temperatures. Technicians should recognize that physical placement, terminal style (spade terminals)and mounting screw locations determine compatibility when sourcing replacements or diagnosing wiring and connector issues for this part.
Common diagnostic indicators include loss of heating, unexpected shutdowns mid-cycle, intermittent heatingor the oven failing to reach set temperatures despite correct thermostat and control inputs. Practical tests include a continuity check at ambient (the device should show near-zero continuity when cold) and a resistance or functional test while applying controlled heat to observe the open transition; corrosion, mechanical shockor repeated over-temperature events often produce a permanently open contact. Typical symptoms and fast checks are summarized below to guide troubleshooting before claiming control board or element failure:
- No heat at all while control signals are present – likely open high-limit or failed connection.
- Oven stops heating mid-cycle or trips only after extended use – intermittent or weak contacts.
- Oven overheats without tripping – possible thermostat stuck closed (safety hazard).
- Visible corrosion or damaged terminals at the thermostat – suspect mechanical failure; replace and retest.
| Item | Description |
|---|---|
| Normal state | Normally closed at ambient; opens at the specified over-temperature limit to cut power. |
| Quick test | Continuity at ambient (closed) and opens when heated above trip point; infinite resistance indicates failed-open. |
Compatibility, Replacement Procedures, Installation Best Practices and Post-Installation Troubleshooting
The 318578506 Frigidaire Oven High Limit Thermostat is a safety cutout designed to interrupt the heating circuit when localized oven temperatures exceed its calibrated trip point. In normal operation the device presents a closed circuit and opens at or above its rated temperature to remove power from the bake/broil elements or to signal the control board to disable heating. Compatibility requires matching the thermostat’s rated trip temperature, terminal type (spade terminals, lead length, and insulation)and mounting interface to the oven model; substituting a thermostat with a different setpoint, terminal style, or mounting arrangement can produce nuisance trips, failure to protect the ovenor unreliable electrical connections. Many units are mechanically self-resetting while others are one-time thermal fuses, so verify the specification for the 318578506 Frigidaire Oven High Limit Thermostat against your model before installation.
Standard replacement procedures and installation best practices reduce field failures: disconnect power, document and label wire locations, use a continuity meter to confirm open/closed state at ambient temperatureand secure the replacement using the original mounting point to maintain correct thermal coupling to the chassis. Route and secure leads away from heating elements, use insulated high-temperature connectors or properly crimped spade terminalsand avoid soldering connections that sit in high-temperature zones. After installation, verify function by running a controlled heat cycle: confirm continuity opens near the specified trip range (or that the oven ceases heating at the expected threshold), inspect for intermittent opens under vibration or thermal cyclingand monitor heater current and control signals if the thermostat still trips unexpectedly. If problems persist, inspect surrounding insulation and element alignment for hotspots and check the control board for spurious commands that might mimic thermostat behavior.
- Common symptoms and quick checks: oven fails to heat (check continuity at ambient), oven cuts out at normal temperatures (compare thermostat trip rating), intermittent heating (inspect connectors and lead routing).
- Quick installation checks: verify terminal fit, confirm secure chassis mountingand ensure leads are not contacting the element.
- Troubleshooting aids: use a multimeter, heat gun for controlled heatingand compare measured behavior to the thermostat’s specified trip temperature.
| Item | Description |
|---|---|
| Part | 318578506 Frigidaire Oven High Limit Thermostat – OEM-specified high-limit safety thermostat |
| Function | Opens circuit at rated temperature to prevent overheating; either self-resetting or non-resetting depending on design |
| Mounting/Terminals | Match bracket and terminal type (spade size, lead length) to ensure correct thermal coupling and reliable electrical connection |
| Common failure modes | Open circuit due to corrosion or thermal fatigue, intermittent contacts from loose terminals, nuisance trips from incorrect part rating or poor mounting |
Q&A
What does the 318578506 Frigidaire oven high limit thermostat do?
The high limit thermostat is a safety device that opens its contacts if the oven temperature rises above a manufacturer‑specified limit. Its job is to cut power to heating elements or the control system to prevent overheating, firesor damage to oven components. It is indeed not the same as the oven temperature sensor (NTC),which provides temperature feedback for regulation.
What are common symptoms that the high limit thermostat is failing?
Common signs include the oven not heating at all even though control settings are correct,the oven shutting off mid‑cycle with no error code,or intermittent heating (works sometimes,then fails). if the thermostat has an open circuit at room temperature it has typically failed. Persistent overheating can also indicate a failed thermostat that does not open when it should.
How can I test the 318578506 high limit thermostat?
Turn power to the range off. Locate the thermostat and disconnect its wires. Use a multimeter set to continuity or low ohms. At room temperature the thermostat should show continuity (near 0 Ω). If it reads open (infinite resistance) cold, it is defective. For further testing you can carefully heat the thermostat (heat gun) to verify it opens at its trip temperature, but consult specs and use caution-do not exceed safe temperatures. Always remove power before reconnecting.
Where is the high limit thermostat located on a Frigidaire oven?
Location varies by model, but it is indeed typically mounted on the back wall of the oven cavity or on the rear of the appliance behind the back access panel, near the heating element or control area. You may need to pull the oven out of the cabinet and remove the rear or inner back panel to access it. Consult your model’s service manual for the exact location and disassembly instructions.
Is the 318578506 the same as the oven temperature sensor or thermostat in the control board?
No. The 318578506 is a high limit thermostat (safety cutoff) and should not be confused with the oven temperature sensor (an NTC thermistor) used by the control board to regulate cooking temperature. The high limit is a mechanical/electrical cutoff that opens at a fixed high temperature; the sensor provides variable resistance for temperature control.
How arduous is it to replace the high limit thermostat and what precautions should I take?
Replacement difficulty is moderate. You must disconnect electrical power, remove panels to access the part, note or photograph wire locations, disconnect wires, remove mounting screwsand install the new part in reverse order. Precautions: disconnect power at the breaker or unplug the range, allow the oven to cool, avoid damaging insulation or wiring, and ensure all connections are secure. If you are not pleasant with appliance electrical work,hire a qualified technician.
How do I ensure the 318578506 is compatible with my Frigidaire model and where can I order it?
Verify compatibility by checking your appliance’s model number (usually on a tag behind the door, on the frameor on the rear panel) and cross‑referencing that model with the part number 318578506 on Frigidaire’s parts website or a reputable parts supplier. Many suppliers provide a “fits models” list. Buying OEM (Frigidaire) parts is recommended for correct fit and performance.
What could cause the high limit thermostat to trip repeatedly after replacement?
Repeated tripping indicates an underlying problem rather than the thermostat itself, such as a failed control relay that doesn’t cut power, a shorted heating element, poor airflow from a blocked vent or failed convection fanor a faulty temperature sensor/control causing the oven to overheat. After replacing a faulty high limit, diagnose the heating circuit and controls to find why the oven exceeded the safe temperature.
In Conclusion
the 318578506 Frigidaire Oven High Limit Thermostat functions as a critical safety and control component that monitors and limits oven temperature to prevent overheating.By interrupting power to heating elements when temperatures exceed safe thresholds, this thermostat helps protect internal components, maintains more consistent cooking performanceand reduces the risk of fire or damage associated with uncontrolled heat.
Because symptoms of a failing high limit thermostat-such as erratic temperature behavior,frequent shutdowns,or failure to reach set temperatures-can overlap with other control or sensor issues,proper diagnosis is essential. Accurate testing and inspection, adherence to Frigidaire’s diagnostic proceduresand use of the correct replacement part help ensure reliable operation. When replacement is necessary, selecting the appropriate OEM or equivalent part and verifying correct installation and calibration will restore safe temperature regulation and appliance performance.
Timely and informed attention to the 318578506 high limit thermostat preserves oven safety, efficiencyand longevity. For moast users, consulting the manufacturer’s service data or a qualified technician provides the best assurance that diagnosis, replacement, and post-repair testing are completed safely and effectively.
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