318578506 âFrigidaire Oven High Limit Thermostat is a temperature-actuatedâ safety device used â˘in many Frigidaire electric ovens; â˘it is a⤠high-limit thermostat â˘(a temperature âcutâout) that âŁopens at a âpredetermined threshold to interrupt power to âheating circuits when âthe oven or appliance chassis exceeds a safe â¤temperature. Physically, the component is typically aâ small switch assembly with a temperature sensor or âbimetal elementâ adn spade terminals or aâ connector, âŁdesigned to be mounted⤠close âto the oven cavityâ or heating âŁelements and to operate without âuser adjustment.
Inside the appliance, the â¤high limit thermostatâ functions as âan overtemperature protection âŁlayer⢠that⣠interfacesâ with the bake/broil heating âŁelements, relay/contactor âŁor⣠control⣠board outputsand, âŁin gas units, with the gas valve⤠circuit. It is distinct from the⣠oven temperature control or probe â¤used for normal⢠temperature regulation: the high limit is aâ safety âcutâout that prevents sustained â¤overheating caused âŁby âcontrol⣠failures, blocked ventilation, failedâ fansor insulationâ breakdown. Its status âcan affect âelement energization, control error reportingand overall thermal managementand it is indeed âusually placed so it senses⢠either the⤠cavity temperature or the internalâ chassis temperature most likely to⣠indicate a hazardousâ condition.
This article â˘explains how the 318578506 high limit thermostat operates, â˘how âto determine âcompatibility and âŁcorrectâ mounting for replacement, common failure â˘modes and symptoms to look âŁfor, practical troubleshooting â˘checksâ for âtechnicians (continuity, wiring and connector inspectionand temperature verification)and⢠considerations whenâ selecting â˘and installing a replacement part. Readersâ will gain technical context to diagnose â¤issues related⢠to overheatingâ or lossâ of heat and to make informed decisions about⣠testingâ and⢠replacing this âŁsafety component while⣠observing appropriate electrical⤠and safety procedures.
Tableâ of Contents
- Function and Role of the HighâLimit Thermostat⤠in Oven Thermal Safety and⤠Control Systems
- How the 318578506 âFrigidaire Oven âHigh âLimit Thermostat Works: Sensing Mechanism, Contact Operationandâ Integration with⣠control Circuits
- Diagnostic Indicators andâ Common â˘Failure⣠Symptoms of HighâLimit⤠Thermostat â˘Faults
- compatibility,â Replacement Considerationsand Installation Procedures⤠for⣠the â¤318578506 HighâLimit Thermostat
- Q&A
- The Conclusion
Function and⤠Role of the HighâLimit Thermostat⣠in Oven Thermal Safety and Control⣠systems
The 318578506 Frigidaire Oven High Limit Thermostat â is a â˘fixed-setpoint safety device that interrupts heater power when internal â˘temperatures exceed a manufacturer-specified threshold. Functionally âitâ is a normally-closed thermal cutout that opens at its trip temperature to prevent⢠sustainedâ overheating of the oven cavity âor control compartment; once open⢠it⣠disables the heating âcircuit until the â˘thermostat cools âbelow âits reseat temperature (or is manually reset if of âa latching â¤type).Technicians should treatâ this part as a last-line protection separate from the oven’sâ temperature controlâ thermostat and electronic â˘controlâ board: verify electrical continuity at room temperature with a meter,â confirm correct connector and âŁmounting⣠orientation,â and â˘replace⢠with the exact part or an â˘approved âŁequivalent to âmaintain correct trip characteristics and mechanicalâ fit.
In a broader thermal â˘control architecture the high-limit thermostat âŁprovides an self-reliant overtemperature interlock that âcomplements the primary temperature regulator and âthermistor/RTDâ feedback loop.â It⣠is commonly mounted â˘near heating elements or the control housing so its thermal âtimeâ constantâ reflects â¤worst-case heating scenarios; because âit⢠is a binary device rather than a proportional sensor,its role is to fail-safe rather thanâ regulate.â Typical field practice includes checkingâ for open-circuit â˘failure (oven produces no⤠heat), shorted failure (potential for overheating)andâ thermal cycling behaviour underâ load. When replacing the thermostat, isolate mains power, document âwire positionsand ensure the replacementâ maintains the same electrical rating and physical⢠mounting⢠to avoid creating a compatibility or âsafety hazard.
- Common âsymptoms: no heat (open), uncontrolled heating (failed closed), âŁor intermittent tripping under⢠normal use.
- Service checks: continuity at⤠ambient, visual inspection for heat damageand correct terminal/wire harnessâ fit.
- Installation notes: match electrical rating âand mounting; do not attempt â¤to alter trip calibration.
| item | Description |
|---|---|
| Function | Fixed-setpoint thermal âŁcutoutâ that interrupts âpower âto⢠heating elements when â¤overheated |
| Behavior | Normally closed; opens at trip temperature to protect against ârunaway⢠heat |
| Compatibility | Designed for âspecified⣠Frigidaireâ oven âmodels-confirm connector, mounting,⤠and electrical rating before replacement |
How the 318578506 Frigidaire oven High Limit Thermostat Works: Sensingâ Mechanism, Contact Operationand Integration with⤠Control Circuits
The 318578506 Frigidaire Oven âHigh Limit Thermostat is âa⣠non-adjustable safety thermostat that âŁmonitors enclosure â˘andâ insulation temperatures using a âŁbimetal sensing â¤element.â As⤠the oven temperature rises,the⣠bimetal disc flexes; at the âŁthermostat’s â˘setpoint the disc mechanically opens the electrical contacts,interrupting theâ circuitâ that supplies power to heating⤠elements orâ the control relay. In practice this component prevents runaway heat caused by failed relays, stuck cyclesor insulation faults, âand technicians verify its operation by â˘checking for â¤cold continuity and visually inspectingâ the mounting and terminal connections before replacing it with a â¤partâ that⢠matches the original setpoint â˘andâ terminal style.
Theâ contact operation is⤠typically normally-closed â¤during normal operation and opens on anâ over-temperature â¤condition, âŁplacing the high-limit inâ series with either â¤the heaterâ power line â˘or the control board’s relay coilâ so⤠heat calls are⤠blocked⢠immediately when âit trips. â¤Integrationâ details matter: some ovens⢠use the high-limit purely as a hard⣠cutoutâ inâ the element circuit,⤠while others routeâ the switch to the controlâ boardâ so aâ fault can be⢠logged and user-interface lockouts applied. For⤠troubleshooting and compatibility âchecks,measure âcontinuity atâ ambientâ temperature,compare the stamped setpoint and terminal arrangement to the replacement,and inspect wiring forâ signs ofâ overheating or corrosion;⤠replacing the thermostat âŁwith â¤a unit of incorrect setpoint orâ terminal type âcan leave the oven unprotected or nonfunctional.
- Common diagnostic checks: cold continuity test, visual âcontact inspection,⣠compare stamped setpoint, verify correct terminal type and mounting location.
| Item | Description |
|---|---|
| Setpoint | Fixed âtemperature âŁat wich contacts open (match OEM rating) |
| Contact type | Normally-closed bimetal switch that opens on over-temperature |
| Typical terminals | Spade lug or screw terminals; â˘verify physical fit and wiring polarity |
Diagnostic âIndicators and Common Failure âSymptoms of⢠HighâLimit âThermostat Faults
The 318578506 Frigidaire â¤Oven High Limit Thermostat â˘is a âŁsafety cutoff device that monitors internal oven temperature â¤and opens⤠its internal âswitch when a predetermined overâtemperature condition occurs. In operation it âis typically a normallyâclosed bimetal or thermal switch mounted near the oven cavity or heating element; when the âsensing element⣠reaches its trip threshold the âcontact opens to interrupt the heating circuit or âŁsignal the control â˘board,â preventing sustained overheating.Compatibility is⣠modelâspecific-this part is used as a direct âreplacement in â˘many Frigidaire ranges and wall ovens but should be crossâreferenced with the appliance model numberâ or serviceâ manual to ensure matching mounting,terminal âtype,and trip characteristics.
Technically, common failure modes includeâ a contact that has failed open at ambient temperature, a contact âthat opens intermittently⤠under loador a sensor that trips atâ too lowâ a temperature. For practical diagnostics, first disconnect mains power and then check continuity acrossâ the thermostat terminals with a multimeter; a healthy âŁhighâlimit thermostat âwill⢠show âcontinuity â˘(near 0 â¤ÎŠ) âŁat room temperature and will⣠open (infinite resistance) when deliberately heatedâ above âŁitsâ trip point â˘duringâ a controlled test. Observable symptoms â˘useful to technicians and owners include â˘the âoven ârefusing to heat, premature shutdownsâ during bake cyclesor unstable thermostat control leading to wide temperature swings; verify wiring, connectorsand any related limit switches⤠or controlâ board inputs before replacing the partâ to confirm the thermostat is⤠the âroot cause.
- Oven will ânot heat at⤠all (no continuity at room temp)
- Oven heats âthen suddenly⤠shuts off (intermittent open)
- Inability⢠to reach or⤠maintain target⤠temperature (nuisance tripping)
- Error codes orâ control lockouts indicating overâtemperature or â¤sensor â¤faults
| Item | Description |
|---|---|
| Normal state | Normally closed at ambient; âŁconducts to allow heating under normal âoperation |
| Failed open | Shows no continuity at room temperature; oven âwill not â˘heat |
| Test method | power â¤off, disconnect wires, â˘measure continuity; heat âsensor⤠to verify opening behavior |
Compatibility, Replacement Considerationsandâ Installation Procedures âŁfor the 318578506⢠HighâLimit Thermostat
The 318578506 Frigidaire Oven High Limit⢠Thermostat is a temperatureâsensitive safety âcutout that interrupts the oven’s control circuit when local⤠temperatures exceed its calibrated trip⢠point, protecting insulation, â˘wiringandâ electronic controls. âIn normal conditionsâ the device is a âclosed contact at âambient temperature and opens when âthe sensing⤠element âŁreaches the limit⢠temperature; some versionsâ also âinclude âa manual reset. âCompatibility⤠depends onâ matching mechanical â¤mounting, terminal type and spacingand theâ device’s specified âŁtrip temperature, âsoâ technicians should verify the replacement part’s physical dimensions and electrical characteristics â¤against âthe originalâ before installation to ensure proper âbehavior inâ the â˘oven environment.
When replacing the âhighâlimit thermostat, follow safe⤠electrical practices and confirm âŁthe replacement matches the original’s trip characteristics and mounting âstyle.Typical installation â¤steps include removing theâ oven access panel, documenting â˘and disconnecting âŁthe wiring,â measuring cold continuity âŁwith an ohmmeter⣠(normally⣠closed should read low resistance at ambient), fitting the new thermostatâ so the sensing element has the same contact withâ the oven â˘chassis⢠or insulationand then restoring power to⣠observe normal operation; after installationâ perform an operational check by⤠running a âbakeâ cycle and verifying stable control and no nuisance cutouts. If the original part was âŁmanualâreset, select a likeâforâlikeâ replacement; â¤ifâ the oven exhibited overheating âor intermittentâ shutdowns, also inspectâ adjacent insulation andâ control relays to rule âŁout â¤secondary causes.
- Power⣠off: Disconnect mains â¤before accessing internal⢠parts.
- Document terminal labeling and â¤take photosâ of wiring âbefore removal.
- Measure continuity at âambient; âexpect aâ lowâohmâ reading if normally closed.
- Match mounting bracket,⤠terminalâ typesand trip temperature whenâ sourcing a replacement.
- Secure sensing element so it contacts the same chassis point andâ does not touch heating elements.
- Perform⣠aâ functional bake âŁtest after reassembly to confirm correct operation.
| Item | Description |
|---|---|
| Function | Overâtemperature â¤safety cutout that opens â¤the âcircuit at a specified trip temperature. |
| Mounting & terminals | bracket or clip mount; spade or â˘screw âterminals-must match original âspacing andâ connector type. |
| Test/expected continuity | Normally closed at ambient (low ohms);⣠opens when heated to the rated limit-verify â¤with controlled heating âand multimeter. |
Q&A
What âis⣠the 318578506 âFrigidaire Oven âHighâ Limit Thermostat and what does it do?
the 318578506 is âa highâlimit â(safety) thermostat used on âsome Frigidaire ovens. It isâ a fixed bimetal â˘temperature âŁcutoff switch that⤠opens when the oven or⢠control âcompartment â¤reaches an unsafe high temperature. Its âjob is⢠to interrupt power toâ theâ heating circuit (or signal âthe control) to prevent overheating and potential fireâ or component⢠damage.
How do I know if 318578506 is⢠the correct replacement part âfor my oven?
Confirm the oven’s full modelâ number (usually on a âtag inside the oven âdoor frame or behind the â˘kickplate) and crossâreferenceâ it⢠with Frigidaire parts âŁlists or an⢠authorized parts dealer. Compare the âŁpart number, mounting⤠style, âŁelectrical connector type (spade size/quantity)and physical dimensions.⢠If in doubt, use⢠Frigidaire’s official âparts â¤lookupâ or â˘contact â˘support â¤to verify compatibility before buying.
What â˘are common symptoms⤠of âa failing highâlimit âthermostat?
Typical symptoms include the ovenâ refusing to âheatâ at all, the bake orâ broil element not receiving power, the oven shutting off midâcycleor âŁthe control reporting an â˘overâtemperature fault. â˘A failed âhighâlimit most commonly fails âopen (noâ continuity), which prevents⣠the⣠heating circuitâ from energizing.
How can I test the highâlimit thermostat safely?
always disconnect power to the appliance before â¤testing. âAccess the thermostat and disconnect its wires.With a â¤multimeter set to continuity or low ohms, check âŁacross the two⣠terminals at room âtemperature-a healthy âŁhighâlimit is normally closed and should show continuity (near⤠zero ohms). Gently heat the sensor portion⣠(hairâ dryer, heat gun at distanceor controlled⢠heat) and watch the meter:⢠itâ should open (lose continuity) when it reaches its trip⣠temperature. If itâ never shows continuity âwhen coldâ or ânever opens when heated,â it should be replaced.
Can I âŁadjust or calibrate the⢠318578506 thermostat if⢠my oven temperature is⣠off?
No. The highâlimit thermostatâ is a⤠fixed â¤safety device and is not intended for temperature calibration. â˘If your oven is running âtoo hot or too cold for normal â˘cooking, âthe cause is usually the oven âthermostat/sensor or the âelectronic control, not theâ highâlimit. Replace the⤠highâlimit only if it fails its âsafety function.
How âdo I replace the 318578506 âhighâlimit thermostat?
Turn off and disconnect power to the⤠oven (unplug or switch off âŁthe circuit breaker). Removeâ access â¤panels to reach the thermostat, note or label wireâ positions, then disconnect the spade terminals and remove the mounting screw/bracket. Installâ the new thermostat in the same orientation,â secureâ itand reconnect â˘the wires âto the same⣠terminals. âReassemble panels, â¤restore power, âand testâ the oven. If you’re not comfortable working on â˘electrical appliances, hire âa qualified â˘technician.
Are there âŁspecial wiring or⢠connector considerations⢠when⣠replacing âŁthis part?
Theâ highâlimitâ typically uses â¤1/4″ (6.3â mm)⢠spade terminals. Make sure terminals are clean and âfully seated; replace⤠any corroded or⢠loose connectors.Ensure heatâresistant wiring âis used if âŁyou need to⣠replaceâ pigtails. Always match the original⤠wiring configurationâ so âŁpolarity and⣠grounding (where⢠applicable) remain correct.
Where can â¤I buy the â318578506 and how⤠much â˘should I expect to pay?
You can buy âpart 318578506 from Frigidaire/Whirlpool authorized parts⢠dealers, appliance parts websitesand some⣠online marketplaces. Prices vary by⣠vendorâ but typically fall in aâ modest rangeâ (frequently âŁenough under $60). Forâ safety and fit, prefer OEMâ parts or verified equivalents and verify return policies in caseâ the part is not compatible with your specific model.
The Conclusion
The â¤318578506 Frigidaire ovenâ high limit thermostat serves as a âŁcritical safety â¤and performance component, â¤monitoring internal oven temperature and âŁinterrupting heat if temperatures âŁexceed â˘designed limits. By providing reliable overheat protection, this âthermostat helps preventâ damage to oven elements and wiring, reduces the risk âof â¤fireand supports consistent cooking resultsâ by maintaining safe operating conditions.
timely and accurate diagnosis is essential to distinguish thermostat failure from othre âpotential causes of temperature or safety âissues; â˘replacing âŁthe thermostatâ should be done only âwhen testing indicates it is necessary and with a compatible, quality âreplacement. Relying on â˘manufacturer guidelines or a qualified service technician for evaluation and installation âŁhelps âensure⢠the âproblem is fully âŁresolved and âmaintains appliance safety and longevity.
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