318578506 Frigidaire Oven High Limit Thermostat is a thermal safety switch designed to monitor and interrupt heating circuits when temperatures exceed a preset limit. As a temperature-actuated component-commonly implemented as a bimetal thermostat or thermal cutoff-it is intended to open the electrical circuit to heating elements or to signal the control electronics when an over-temperature condition is detected. The part number identifies the Frigidaire-specific replacement used in compatible electric ovens and ranges.
Inside the appliance the high limit thermostat serves as a last-line safety device that interacts directly with the oven’s heating elements, control boardand relay or power-switching assemblies. It is indeed typically mounted in proximity to the bake or broil element housing or on an oven chassis panel so it can accurately monitor perhaps critical heat buildup; when the thermostat opens it prevents further power delivery to the heating circuit and can also provide a discrete fault input to the control system. As it sits in series with heating control and safety circuits, its correct operation is essential for preventing insulation damage, component failureor thermal runaway in the oven cavity.
In this article readers will find a technical overview of how the 318578506 high limit thermostat functions, guidance for verifying compatibility with specific Frigidaire models, common failure symptoms (such as persistent no-heat conditions, intermittent heatingor tripped safety states), and step-by-step troubleshooting checks including continuity tests and visual inspections. The piece will also cover practical replacement considerations-correct temperature rating, resettable versus non-resettable types, proper mounting and connector practices-and safety precautions to follow when servicing or replacing the component.
Table of Contents
- Function and Role of the Oven High Limit Thermostat in Frigidaire Electric Ovens
- How the 318578506 Frigidaire Oven High Limit Thermostat Operates: Sensing Elements,Contact Behavior,and Electrical Integration
- Common Failure Symptoms and Diagnostic Tests for High Limit Thermostat Faults
- Compatibility,replacement Considerations,and Installation Procedure for 318578506 on Frigidaire Oven Models
- Q&A
- To Conclude
Function and Role of the Oven High Limit thermostat in Frigidaire Electric Ovens
The 318578506 Frigidaire Oven High Limit Thermostat is a temperature-actuated safety cutout installed in the oven cavity or rear oven chamber.It functions as a normally-closed, temperature-sensitive switch that opens when a sustained over-temperature condition occurs, interrupting power to the bake/broil elements or the control relay output to prevent thermal runaway if the primary temperature control fails. Unlike the oven thermostat that cycles to maintain setpoint, the high limit is designed to respond only to excessive temperatures and provide a hard safety interrupt rather then fine temperature regulation.
In normal operation the device shows continuity at ambient temperature and only opens when the measured temperature exceeds its set threshold; some designs remain open until the unit cools while others require replacement if mechanically latched.Proper replacement requires matching the OEM part number to ensure the correct trip characteristics, terminal type and mounting orientation, so technicians typically replace the component with the exact 318578506 Frigidaire Oven High Limit Thermostat to maintain intended safety behavior. Common field checks include a continuity test with power removed (continuity at room temperature, open when heated), inspection of mounting and sensor exposure for insulation or airflow obstructionsand observing symptoms such as immediate loss of heat, intermittent heating, or an oven that reaches temperature then shuts off and will not restart until cooled.
- No heat or immediate shutdown: check continuity with power off; an open circuit at room temp indicates a failed cutout.
- intermittent heating or shutdown after reaching temperature: verify sensor exposure and control board faults can cause nuisance trips.
- Bench test: remove the unit, disconnect powerand verify continuity at ambient; do not perform live resistance checks on installed unit.
- Installation: match terminal style and mounting orientation to avoid false trips caused by poor thermal coupling.
| Item | Description |
|---|---|
| Part | 318578506 Frigidaire Oven High Limit thermostat |
| Function | Temperature-actuated safety cutout that interrupts heating circuit on sustained over-temperature |
| Terminals | OEM-specific spade terminals; confirm size and orientation before replacement |
| Diagnostics | Continuity at ambient; open when heated (bench test). Replace if open at room temperature or if nuisance trips persist |
How the 318578506 Frigidaire Oven High Limit Thermostat Operates: Sensing Elements, Contact Behaviorand Electrical Integration
The 318578506 Frigidaire oven High Limit Thermostat uses a bimetal sensing element that reacts to rising oven-cavity temperatures and mechanically opens its internal contacts at a predetermined trip point. In normal operation the contacts are normally closed, providing a direct continuity path to the heating circuit or to the control relay; when the bimetal disc reaches the set limit it snaps open to interrupt power, acting as a non-adjustable safety cutoff rather than a temperature regulator. Because this component is a protective device, its intended behavior is an absolute open condition at the trip temperature; it should not cycle like an oven control thermostat does during temperature control periods.
Electrically, the part is installed in series with the element circuit or in the control board’s safety loop and must match the oven’s terminal configuration and current/voltage rating to function safely. Technicians typically verify the device with a multimeter (continuity at room temperature, open at elevated temperature) or by observing that the control reports an over-temperature fault when the limiter opens; a limiter that reads open at room temp or fails to open under heat requires replacement.When replacing the unit, confirm terminal type, mounting bracketand the manufacturer’s specification so the safety cutoff isolates the correct circuit without introducing excessive resistance or lose connections.
- Typical diagnostic checks: continuity at ambient temp, controlled heating to observe opening, visual inspection for burn or deformation.
- Failure symptoms: oven not heating (open), oven not shutting off (rare if other controls fail)or control board fault codes indicating safety cutoff.
- Installation notes: match terminal lug style and secure mechanical mounting to ensure accurate temperature sensing and reliable contact operation.
| item | Description |
|---|---|
| Sensing element | Bimetal disc, fixed trip designed to deform and open contacts at a preset temperature. |
| Contact behavior | Normally closed at ambient; opens on trip to interrupt heater/control circuit. verify with continuity and applied heat. |
Common Failure Symptoms and Diagnostic Tests for High Limit Thermostat faults
The 318578506 Frigidaire Oven High Limit Thermostat is a safety cutoff device that monitors enclosure or insulation temperatures and opens its contacts when temperatures exceed a designed threshold, interrupting power to heating elements or control circuits. In normal operation the thermostat is a normally closed temperature switch at ambient oven temperatures and only opens on sustained over-temperature conditions; common failure modes include contact welding (stuck closed), contact burn or corrosion (stuck open)or mechanical drift that changes the trip point. Technicians should confirm mechanical fit and wiring harness compatibility with the oven’s model number before replacement and be aware that this thermostat is intended as a safety device, not as a primary control for regular cycling during bake or broil cycles.
- Oven will not heat at all despite control calls for heat – check for an open high limit (no continuity at room temp).
- Oven cuts out mid-cycle or cycles irregularly – intermittent high limit operation or thermal drift.
- Visible scorching, melted insulationor discolored terminals - inspect for thermal damage and replace.
- Continuity present at room temperature but opens at elevated temperature during bench test – indicates correct operation.
| Item | Description |
|---|---|
| Room-temperature reading | Normally closed: low resistance/continuity between terminals when cool. |
| Trip behavior | Opens circuit at its rated limit; bench test with controlled heating should show an open circuit when the thermostat reaches its trip temperature. |
Diagnostic testing follows a safety-first procedure: disconnect mains power, access and unplug the thermostat harness, then measure continuity with a multimeter across the two terminals. A healthy high limit shows continuity at ambient temperature; a permanent open indicates a failed thermostat. For functional verification you can warm the sensing area (heat gun or controlled oven warming while monitoring temperature with an autonomous probe) and observe the switch opening at the expected limit. Also inspect mounting, element routing, and nearby insulation for heat sources that could prematurely actuate the thermostat; replacing the component without addressing an external overheating cause can produce repeated failures.
Compatibility, Replacement Considerationsand Installation Procedure for 318578506 on Frigidaire Oven Models
The 318578506 Frigidaire Oven High Limit Thermostat is a temperature-sensing safety device that electrically interrupts the heating circuit when the oven enclosure reaches its factory-set high limit. Functionally it is indeed a normally closed thermal switch that opens at a predetermined temperature to protect wiring, insulation, and control electronics from sustained overtemperature. Compatibility depends on the thermostat’s mechanical mounting, terminal type (quick-disconnect spades vs. solder lugs), and its electrical/thermal specifications; replacing the part requires confirming the replacement unit matches the original’s terminal layout and trip characteristics so it provides the same protective behavior in the oven model in question.
- Symptoms to confirm: oven fails to heat because the thermostat stick is open at room temperature, intermittent cut-out of elementsor visible heat damage around the original device.
- Diagnostic checks: perform a cold continuity test with a multimeter (verify continuity at room temperature),inspect mounting for proper thermal contact,and compare connector style and bracket orientation to the factory part.
- Basic replacement steps: disconnect power, remove rear panel, note wire routing and terminal assignments, unmount the old thermostat, install the new unit ensuring tight thermal contact and correct terminal seating, then restore power and perform a controlled functional test with an oven thermometer.
| Item | description |
|---|---|
| part | 318578506 frigidaire Oven High Limit Thermostat – high-limit thermal cutoff used in select frigidaire ranges |
| Test | Continuity at ambient; opens above manufacturer-specified temperature (verify with service literature) |
| Installation note | Match mounting bracket,terminal type,and orientation; ensure firm thermal contact with chassis for accurate sensing |
Q&A
What is the 318578506 Frigidaire oven high limit thermostat and what does it do?
The 318578506 is a safety thermostat (also called a high-limit thermostat or temperature cutoff) used on certain Frigidaire ovens. It is a normally closed thermal switch that opens when the oven or a control circuit reaches an over-temperature condition, cutting power to heating elements or control circuits to prevent overheating and possible fire or damage.
What symptoms indicate the high limit thermostat is failing?
Common symptoms include: the oven not heating at all (even though controls are set correctly), intermittent heating or immediate shutoff of the bake element, the oven light staying on without heatingor error codes on digital models that refer to temperature or safety devices. Because it’s a safety device, failure is often an open circuit (no continuity) at normal temperatures.
how can I test the high limit thermostat safely?
Disconnect electrical power to the range first.Remove access panels to reach the thermostat and disconnect its wiring harness. Use a multimeter set to continuity or low-ohms: at room temperature the thermostat should show continuity (near 0 ohms). If it is indeed open (infinite resistance) at room temperature it is highly likely failed. Some technicians also verify that the thermostat opens when heated to its trip temperature, but that should be done with caution using proper tools and specifications-do not test it live on mains voltage.
What resistance or reading should I expect when testing it?
At normal room temperature a good high limit thermostat will read as a closed circuit, typically near 0 ohms or will give a continuity beep on a meter. It is indeed not intended to read a precise resistance value like a thermistor; the crucial check is that it is closed at ambient temperature and opens at or above its rated trip temperature (the trip temperature is part-specific and printed on the component or in the parts spec).
Where is the thermostat located and how challenging is replacement?
Location varies by model, but the high limit thermostat is usually mounted inside the rear of the oven cavity, on the back wall of the oven chassisor near the bake element on the rear panel. Replacement typically requires removing the oven back panel or broiler drawer and disconnecting two wires; the part is usually secured with screws or bracket. Basic hand tools (screwdriver, nut driver) and powering the unit off are all that’s required for a competent DIYer. If you are uncomfortable working with household mains wiring or disassembling the oven, hire a qualified appliance technician.
is this thermostat adjustable or can it be calibrated?
No – the high limit thermostat in ovens is normally a fixed-temperature safety switch and is not adjustable or intended to be calibrated in the field. If it trips prematurely or no longer holds closed at normal temperature, it should be replaced with the correct part number.
How do I know if the 318578506 is the correct replacement part for my oven?
Verify compatibility by checking your oven’s model number and cross-referencing it with Frigidaire parts lists or an authorized parts supplier. The model number of the appliance (usually on a tag inside the oven door frame or on the rear) is required to confirm the correct thermostat. Do not substitute a different thermostat with a different trip temperature or terminal configuration.
Can I bypass the high limit thermostat to get the oven working?
No. Bypassing a high limit thermostat defeats a critical safety device and creates a serious fire and personal-injury hazard. It may also void warranties and violate local electrical or safety codes. the correct remedy for a failed high limit thermostat is to replace it with the specified part.
To Conclude
The 318578506 Frigidaire Oven High Limit Thermostat serves as a critical safety and control component within Frigidaire ovens,monitoring internal temperatures and interrupting power to heating elements if temperatures exceed safe limits.By acting as a failsafe against overheating, this thermostat helps protect the oven’s internal components and reduces the risk of damage or safety incidents while ensuring more consistent cooking performance.
As the high limit thermostat directly affects both safety and functionality, addressing faults promptly is critically important. Symptoms such as unexpected shutdowns, inability to reach or maintain set temperaturesor continuous heating that does not respond to the control settings can indicate thermostat failure or related control issues. Timely attention minimizes the potential for further damage to the appliance and helps maintain safe operation.
Proper diagnosis and, when required, replacement of the 318578506 Frigidaire Oven High Limit Thermostat are essential. Diagnosis typically involves systematic testing of temperature response and electrical continuity and consideration of related components; replacement should use the correct OEM part and follow manufacturer guidelines to preserve performance and warranty coverage. When in doubt, engaging a qualified service technician ensures the repair is performed safely and that the oven is correctly calibrated and tested before returning to service.
the 318578506 Frigidaire Oven High Limit Thermostat is a small but vital component that supports both safety and reliable oven operation. Accurate diagnosis and appropriate replacement, carried out according to manufacturer recommendations, help restore proper function and maintain the safe use of the appliance.
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