318578506 frigidaire Oven High Limit Thermostat is a high-limit temperature cutout used in Frigidaire ovens to provide overtemperature protection. The component is a temperature-actuated safety switch-commonly implemented as a bimetallic or thermal cutout device-that is installed in the oven chassis to open its electrical contacts when a predefined temperature threshold is exceeded.
Inside the appliance, the high limit thermostat serves as a safety interlock rather than a primary temperature regulator. It is typically wired in series with the heating circuit or the control relay coil so that, when the device opens at its trip temperature, power to bake/broil elements or control circuits is removed. It thus interacts directly with the heating elements,relay/contactors or control board inputs and indirectly with the oven temperature sensor and airflow paths; it prevents sustained overheating from failed controls,restricted ventilation,or component malfunctions and protects insulation,wiring and nearby electronics from thermal damage.
In this article you will find a concise technical review of the 318578506 part: how it functions, where it is normally located in Frigidaire oven models, how to confirm compatibility with a specific appliance, common failure symptoms (for example an oven that will not heat or an oven that repeatedly shows fault conditions), basic troubleshooting and measurement techniques (visual inspection, continuity checks, and functional verification under controlled conditions), and practical replacement considerations such as matching trip temperature, electrical ratings, mounting orientation and safe disconnection procedures. The guidance is intended to help technicians,engineers and competent appliance owners assess and address issues while observing appropriate safety precautions.
Table of Contents
- Functional Role and Safety Operation of the oven High-Limit Thermostat
- How the 318578506 Frigidaire Oven High Limit Thermostat Operates, Senses Temperature, and Interfaces with Control Circuits
- Common Failure Symptoms, Measured Electrical Signatures, and Mechanical Indicators for Diagnosis
- Compatibility, cross-Reference, Replacement Considerations, and Step-by-Step Installation Procedure for Service Technicians
- Q&A
- Closing Remarks
Functional Role and Safety Operation of the Oven High-Limit Thermostat
The 318578506 Frigidaire Oven High Limit thermostat acts as a non-adjustable safety cutoff that interrupts electrical power to heating elements or control circuits when internal temperatures exceed a manufacturer-specified threshold. Technically,the device is a normally closed temperature-actuated switch mounted in the oven cavity or insulation channel; as temperature rises past its trip point the contact opens,removing drive to the bake/broil elements or the electronic control board. This part is supplied as an OEM replacement for select Frigidaire ranges, so technicians should verify terminal type, mounting location, and rating against the appliance model before installing to ensure proper mechanical fit and thermal sensing behavior.
In practical operation the high-limit thermostat prevents thermal runaway and limits damage from failed control systems. Common diagnostic steps include checking for continuity at ambient temperature (the thermostat should measure closed) and observing whether continuity opens as the area warms; lack of continuity at room temperature indicates a failed open device. Physical checks-secure mounting, intact terminals, and correct wire routing away from direct element contact-help ensure accurate sensing. Do not bypass this device for testing beyond brief diagnostics; replacing a tripped or failed high-limit thermostat with the correct part and rating restores the designed safety function.
- symptom: Oven elements receive no power – check thermostat continuity at room temperature.
- Symptom: Oven cycles off at low temperatures – thermostat might potentially be opening prematurely or mounted incorrectly.
- Check: Verify terminal style (quick-disconnect vs. screw) and swap only with compatible replacements.
- Safety: Never bypass the thermostat for extended testing; replace defective units rather than permanently bridging.
| Item | Description |
|---|---|
| Function | Temperature-actuated safety cutoff that opens at a manufacturer-specified trip point |
| Electrical | Normally closed contact at ambient; opens on over-temperature to interrupt heater circuit |
| Compatibility | OEM replacement for select Frigidaire ovens-confirm model and terminal configuration |
How the 318578506 Frigidaire Oven High Limit Thermostat Operates, Senses Temperature, and Interfaces with Control Circuits
The 318578506 Frigidaire Oven high Limit Thermostat is a fixed-set mechanical temperature cutoff that senses local oven temperature through a bimetal element or thermally coupled sensing bulb and opens its contact when the calibrated threshold is exceeded. In normal operation the thermostat provides a closed path for the heating circuit (or a feedback line to the control board) and then opens to interrupt power when the local temperature rises above the rated limit; this action prevents sustained overheating of the cavity or internal components. the device typically mounts near the bake element or control cavity so its sensing reflects the area it protects,and its electrical interface is a simple two-terminal switch designed to be placed in-series with the heating relay or the element circuit on legacy and many service-replaceable control systems.
Technically, the thermostat behaves as a mechanically actuated, fixed-threshold switch with inherent hysteresis: the open/close points are separated to avoid rapid cycling around the trip temperature. For troubleshooting and compatibility, technicians should verify terminal type (spade size), mounting flange geometry, and the calibrated trip temperature listed by the manufacturer before replacing the unit. Common practical checks include measuring cold continuity with a multimeter (closed at ambient), confirming loss of continuity after a controlled local heat application, and inspecting wiring and thermal insulation that could cause false trips. Replacements must match the original part’s electrical rating and mechanical fit to ensure correct interaction with the oven’s relay or control board.
- Typical interface: two spade terminals, in-series with heater relay or element.
- Normal state: normally closed at ambient; opens on overtemperature.
- Failure symptoms: oven will not heat,heater remains off after reaching low temperatures,or intermittent heating cycles.
- Service checks: continuity test at ambient and after controlled heating; inspect mounting location and wiring harness.
| Item | Description |
|---|---|
| Type | Fixed-set mechanical high-limit thermostat (bimetal/thermal element) |
| Function | interrupts heating circuit or sends cutoff signal to control when trip temperature exceeded |
| Terminals | Two spade connectors; must match replacement wiring and connector size |
Common Failure Symptoms, Measured Electrical Signatures, and Mechanical Indicators for Diagnosis
The 318578506 Frigidaire Oven High Limit Thermostat is a normally closed thermal safety device used to protect the oven cavity and control electronics from excessive temperatures. Functionally it interrupts the control circuit when the internal temperature exceeds its setpoint, typically via a bimetallic element or thermal cutoff inside a two‑terminal housing that accepts standard spade connectors. Compatibility depends on mounting style, terminal spacing, and trip temperature, so verify the replacement matches the oven model and mounting bracket rather than relying on shape alone.
Common failure modes produce distinct electrical and mechanical signs that help diagnosis. Electrically,a healthy unit shows continuity at ambient temperature and opens (no continuity) when heated past its setpoint; a failing thermostat may show intermittent opening,elevated resistance when closed,or no continuity even when cold. Mechanically, look for burned or charred insulation, melted housing, distorted bimetal parts, corroded terminals, or loose mounting screws. For safe testing, remove power before disconnecting or measuring, check continuity with a multimeter across the two terminals, and confirm the device opens when warmed under controlled conditions; replace the part if it is open at ambient temperature, shows variable resistance, or exhibits visible damage.
- Oven won’t heat or heats erratically – continuity absent or intermittent under test
- Controller fault codes or repeated safety shutdowns – thermostat opens prematurely
- Measured low resistance (~0 Ω) when cold,infinite resistance when tripped – expected electrical signature
- Physical signs: melted housing,warped bimetal,broken/corroded terminals indicate replacement
| Item | Description |
|---|---|
| Cold continuity | Low resistance (near 0 Ω) indicating a closed contact |
| Open at trip | No continuity when heated above the thermostat setpoint |
| Intermittent/high resistance | Variable or elevated ohms when cold signals deteriorating contacts |
| Mechanical damage | Burning,melting,terminal corrosion,or deformation – replace immediately |
Compatibility,Cross-Reference,replacement Considerations,and step-by-Step Installation Procedure for Service Technicians
The 318578506 Frigidaire Oven High limit Thermostat is a fixed-setpoint safety device designed to interrupt power to the bake element if the oven cavity or element assembly exceeds a predetermined overtemperature. This component is a bimetal switch that is normally closed at ambient temperature and opens at the limit to prevent thermal runaway; it is not a modulating control and should not be substituted for the oven temperature sensor or primary control thermostat. Compatibility depends on mechanical mounting, spade terminal spacing, and the specified cutout temperature and voltage rating, so cross-reference the exact Frigidaire model and service sheet before selecting a replacement.
For replacement, technicians should verify continuity at ambient with a multimeter, confirm voltage to the circuit with power removed and lockout applied, and match terminal type and setpoint from the service data. Follow a systematic procedure: disconnect power,access the thermostat location,document and label wiring,remove the old thermostat and any insulating grommet or bracket,install the replacement with the same orientation and secure terminals,restore power,and perform a controlled functional test by running a preheat cycle and confirming normal element cycling and absence of overheating. If the oven continues to overheat after installation, recheck wiring, element integrity, and that the replacement part matches the original specification.
- Disconnect power and lock out before starting.
- Document wire locations (photo or label) and remove access panels.
- verify continuity at ambient; replace if open or intermittently failing.
- Install new thermostat with identical terminal spacing, use proper spade connectors and insulation grommet.
- Restore power and verify oven preheat, element cycling, and no sustained overtemperature.
| Item | Description |
|---|---|
| Function | Fixed-setpoint safety switch that opens on overtemperature to interrupt bake element power. |
| Terminal type | Usually 1/4″ spade terminals; confirm spacing and gender to match harness. |
| Common symptom | Oven shuts off and will not heat or oven overheats if thermostat fails closed or opens intermittently. |
Q&A
What is the Frigidaire part 318578506 (oven high limit thermostat) and what does it do?
The 318578506 is a high‑limit thermostat / safety cutoff used on some Frigidaire ovens. It is a temperature‑sensitive switch (usually a bi‑metal or thermal cutoff device) that opens at a predetermined over‑temperature to interrupt power to the bake element, igniter or control circuit and prevent the oven from overheating.
What symptoms indicate the high limit thermostat may be bad?
Common symptoms include: the oven will not heat at all, the oven heats briefly then shuts off, intermittent heating, or the broil/bake element does not get power. Because it’s a safety device, a failed open thermostat often results in no continuity so the oven won’t energize the heating circuit.
How can I test the high limit thermostat safely?
First disconnect power to the range (turn off the breaker). Remove access panels to reach the thermostat terminals. With a multimeter set to continuity or ohms, check across the thermostat at room temperature-most good high‑limit thermostats will show continuity (very low ohms) when cool. If it reads open (infinite resistance) when cool, it is indeed likely failed. Some technicians also heat the sensor gently (hair dryer) while watching the meter to confirm it opens at the trip temperature, but follow safety precautions and manufacturer guidance.
Is the high limit thermostat the same as the oven temperature sensor or thermostat knob?
No. The oven temperature sensor (also called an oven probe or thermistor) monitors cooking temperature and reports it to the control board. The high‑limit thermostat is a seperate safety device that cuts power if the oven overheats. Replacing the temperature sensor will not fix a failed high‑limit safety thermostat and vice versa.
Can the high limit thermostat be repaired or adjusted, or does it need to be replaced?
High‑limit thermostats are not typically adjustable or repairable. If the device is out of spec (open when cold or not opening at the correct temperature), the correct action is replacement with the specified OEM part (318578506 or an approved equivalent).
How do I replace the 318578506 high limit thermostat?
Turn off power to the appliance at the breaker. Access varies by model (rear panel or oven cavity access panels),so consult the model’s service manual. remove the mounting screws, note the wire connections or take a photo, disconnect the terminals, transfer any insulation or mounting brackets, install the new part, reconnect the wires, and reassemble. Restore power and test operation. If you’re not agreeable working on live circuits or removing panels, hire a qualified technician.
Which Frigidaire models use part 318578506 and how do I confirm compatibility?
Compatibility depends on the oven model and production date. Always confirm by checking your appliance model number and cross‑referencing it with the Frigidaire parts list or an authorized parts distributor.Do not rely solely on visual similarity; ordering by OEM part number and model number avoids incorrect parts.
Is it safe to bypass the high limit thermostat to get the oven working?
No. Bypassing a high‑limit thermostat defeats a critical safety device and can cause overheating, fire or injury. Never bypass or jumper the thermostat. If the part is faulty, replace it with the correct OEM component and follow proper repair and safety procedures.
Closing Remarks
The 318578506 Frigidaire oven high-limit thermostat serves as a critical safety and control component by monitoring oven temperature and preventing overheating. By interrupting power to the heating elements when temperatures exceed safe thresholds, this thermostat helps protect internal components, maintain consistent cooking performance, and reduce the risk of fire or damage from uncontrolled heat.
accurate diagnosis is essential when oven temperature irregularities or safety faults appear; symptoms can stem from sensors, control boards, or wiring as well as the thermostat itself.Verifying the root cause before replacing the part ensures that the underlying issue is resolved and avoids needless expense or repeated failures. When replacement is required, using the correct 318578506 component and following the manufacturer’s specifications help restore proper operation and preserve appliance reliability.
For owners and service technicians alike, balancing careful diagnosis with timely replacement supports safe, efficient oven performance. Engaging qualified technicians or referring to manufacturer guidance for testing and installation helps maintain warranty compliance and safety standards, ensuring the appliance continues to operate as intended.
Professional Appliance Service
If your appliance requires professional diagnosis or repair, visit
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For local appliance service information see
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.
Replacement parts for many appliance models can also be found at
Reliable-Parts-Hub
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