Maytag MER7775WW1 Thermostat (Oven Temperature Sensor) – Diagnose & Replace

Understanding the Problem

Brief explanation: The MER7775WW1 electric range uses an electronic oven temperature sensor (often called the oven thermostat or thermistor) to tell the control board what the oven temperature is. If that sensor fails or its wiring is faulty, the oven will overheat, undercook, or cycle incorrectly. Diagnostic & repair steps: 1) Verify symptoms: note whether the oven runs too hot, too cold, doesn't reach set temp, temperature swings wildly, or shows an oven sensor error. Try a simple bake test (set 350°F for 20–30 minutes) to confirm inconsistent results. 2) Safety first: shut off power to the range at the circuit breaker. Confirm power is off using a non-contact voltage tester or by verifying the oven displays are dark. 3) Access the sensor: open the oven door, remove the oven racks, and locate the temperature sensor — usually a metal probe screwed into the upper left or upper rear interior wall of the oven. Remove the two screws holding the sensor and gently pull it forward a few inches. Follow the wiring back to the back panel to reach the connector. 4) Visual inspection: check the sensor probe for physical damage, and inspect the harness and connector for burnt pins, corrosion, or loose wires. 5) Resistance test (multimeter): set a digital multimeter to ohms (Ω). Unplug the sensor connector from the harness (or remove the sensor). At room temperature (~70°F / 21°C) a typical oven sensor (NTC thermistor) will read around 1,000–1,100 ohms (values vary by model; the key is that it gives a reasonable resistance and changes with heat). Note: resistance should decrease as temperature increases. 6) Live-response test (optional): with sensor unplugged from control board, carefully heat the sensor tip with a hair dryer while watching multimeter resistance — you should see the resistance change smoothly lower as it warms. If resistance is open (OL), stuck, or does not change, the sensor is bad. 7) Check harness and control board: if the sensor reads correctly, test continuity of the wiring harness between the sensor connector and the control board connector. If wiring is good but oven still misbehaves, the control board (infinite relay/relay or software) may be failing. 8) Replace the sensor: if sensor fails the resistance or live-response test, replace it. Remove screws holding sensor in the oven wall, disconnect the two-pin connector, install new sensor, screw it in place (do not over-tighten), reconnect harness, restore power, and run a bake test. 9) Final testing: preheat to 350°F and verify oven reaches and holds temperature within a normal tolerance (±15–25°F). If problems persist, test the bake element for proper continuity and inspect the control board for error codes or visible damage. How to fix (summary): remove power → remove oven racks → unscrew and unplug the oven temperature sensor → test with multimeter at room temp and while heated → if bad, install a matching replacement sensor and retest. If sensor is good but problem remains, inspect wiring and the main control board. Safety note: Always disconnect power at the breaker before working inside the oven. If you are not comfortable working with electrical wiring or testing with a multimeter, hire a qualified appliance technician.

Common Symptoms

Oven overheats or undercooks, oven won't reach set temperature, wide temperature swings, long preheat times, or oven sensor-related error codes.

Common Causes

• Failed oven temperature sensor (thermistor) giving incorrect resistance readings
• Loose, corroded, or damaged wiring or connector between sensor and control board
• Faulty oven control board that misinterprets sensor input or doesn't regulate elements

Popular Parts That Fix This Problem

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Frequently Asked Questions