Mora K878AW cooker: gas hob, electric oven, timer relay, heating element, ignition faults

User question

Mora K878AW

Artificial Intelligence Response

Direct answer to the question

• Mora K878AW is a freestanding combination cooker: 4‑burner gas hob with flame‑failure safety (STOP GAS) + 70 L multifunction electric oven (MF11), typically in white (AW).
• It has 11 oven functions (incl. rapid preheat, convection, grill), electronic touch timer/clock, integrated burner ignition, cast‑iron pan supports, and a bottom storage drawer. Nominal electric input ≈3.2 kW; grill ≈2.7 kW; temperature range ≈50–275 °C; cabinet size 50 (W) × 60 (D) × 85 (H) cm.
• This model has been marketed in the EU and has likely been discontinued; documentation and spare parts remain available via Mora/Gorenje channels and independent spares suppliers.

Key points

• Hybrid appliance: gas hob + 230 V electric oven; timer/clock interlock must be set for oven to heat.
• Typical failure points: oven heating elements, selector switch, thermostat, clock/timer relay, burner thermocouples, ignition module.
• For parts lookup, use the unit’s type plate (Article/Art. No.) rather than the marketing name “K878AW.”

Detailed problem analysis

Device architecture

• Hob (gas):
  • Four gas burners (often small/medium/large/auxiliary) with integrated 230 V spark ignition and thermocouple‑based flame failure devices (STOP GAS). Each valve includes a magnet coil held by thermocouple mV output once the flame heats the tip.
  • Ignition generator: 230 V AC in, multiple HV outputs to ceramic electrodes.
• Oven (electric, MF11):
  • Heating set typically includes: circular convection element around the fan, top/grill element (sometimes split large grill), and bottom bake element.
  • Airflow via a 230 V shaded‑pole convection fan; separate tangential cooling fan may be present for control panel cooling.
• Control:
  • Mechanical function selector (commutator) + mechanical thermostat or electronic thermostat depending on sub‑variant.
  • Electronic programmer (touch timer/clock) with a power relay; if time is unset after a power loss, the relay may remain open, preventing oven heat.

Typical specifications (engineering view)

• Supply: 230 V, 50 Hz (EU). Electric rating ≈3.2 kW (max all oven loads). Grill ≈2.7 kW. Convection element ≈2.0–2.2 kW. Bottom element ≈1.0–1.3 kW.
  • Element cold resistances (R=V²/P, at 230 V):
  • 2.0 kW: ~26.5 Ω
  • 1.3 kW: ~40.7 Ω
  • 2.7 kW (grill): ~19.6 Ω
• Gas: configured from factory for NG (~20 mbar) or LPG (28–30/37 mbar) depending on SKU; jets (nozzles) are orifice‑specific.

Failure modes and diagnostics

• Gas hob:
  • Ignition clicks but no light: verify cap/crown seating, clean electrode and burner ports, check for moisture after cleaning. Inspect HV leads for carbon tracking; test ignition module supply (≈230 V) and output (visible spark).
  • Flame dies when knob released: thermocouple circuit. Clean the thermocouple tip; ensure flame envelopes ~8–10 mm of the tip. Measure thermocouple:
  • Open‑circuit: ~15–30 mV after 30–60 s flame.
  • Loaded (at valve magnet): typically ≥8–12 mV required. If below, replace the thermocouple or the magnet coil as indicated.
• Electric oven:
  • “Oven cold, light/fan OK”: very often the clock/timer interlock. Set the time; listen for relay click when turning the thermostat on. If no click and no element voltage, the timer PCB/relay is suspect. For diagnosis only (qualified personnel), bridging timer L‑in to L‑out proves the interlock path.
  • One function cold, others OK: failed element. Isolate one terminal and measure R (see above). OL/∞ indicates a blown element. Inspect for spade terminal heat damage and replace dodgy connectors with high‑temp 6.3 mm crimps.
  • Uneven heat / overshoot: thermostat failure or poor fan operation. Check fan free‑spin and winding continuity (hundreds of ohms typical for shaded‑pole; compare to replacement spec). Verify thermostat cut‑in/cut‑out with a thermocouple probe at 180 °C setpoint.
  • Intermittent heat: worn selector (commutator) causing arcing/carbonized contacts. Visual signs: browned plastic, pitted terminals. Replace switch; transfer wires one‑by‑one per diagram.
• Nuisance tripping/burnt terminal block:
  • Inspect mains terminal block at the rear for heat damage. Loose screws create high‑R joints. Replace block and ring‑crimp conductors; torque to spec.

Parts and identification

• Always capture the full data from the type plate (usually inside the door frame or behind the drawer): Model, Art. No., SN, gas category. The Art. No. maps to the correct spares (elements, thermostat, selector, timer, fan, ignition generator, thermocouples).
• Common spares (examples by description; verify by Art. No.):
  • Convection element (round), top/grill element, bottom element.
  • Convection fan motor assembly.
  • Electronic programmer/timer module with relay.
  • Ignition generator (multi‑output), spark electrodes, hob thermocouples.
  • Door hinges and gasket; telescopic runners.

Installation and electrical considerations

• EU appliance: 230 V 50 Hz. In North America, operation requires a correctly wired 240 V branch circuit and frequency tolerance; however, the product is not UL/CSA listed, and gas fittings, regulators, and approvals differ. Using EU gas appliances in the US is not recommended without manufacturer‑approved conversion and local code compliance.

Current information and trends

• This model family is widely cataloged by EU retailers and has been flagged as discontinued, with documentation and aftermarket spares still stocked.
• Trend: hybrid cookers (gas hob + electric multifunction oven) remain popular in 50 cm width for compact kitchens; newer lines add catalytic liners, better door insulation, and more robust electronic timers.

Supporting explanations and details

• Why the timer blocks heating: The programmer’s relay is in series with the line feed to the function selector. If the timer is unset or its relay fails, the selector and thermostat never pass power to elements, mimicking multiple “failed elements.”
• Element resistance math example: A 2.2 kW ring element at 230 V should read R≈(230²/2200)=24.1 Ω. If your meter shows ~24–26 Ω, it’s healthy; if OL, replace.
• Thermocouple test tip: Heat with a small torch while measuring mV; if it reaches spec but the valve won’t hold, the valve magnet is suspect.

Ethical and legal aspects

• Gas work must be performed by a licensed gas technician per local regulations (e.g., EU: EN 30, EN 60335; US: NFPA 54/ANSI Z223.1, local mechanical codes).
• Electrical work should follow IEC 60364 (EU) or NEC (US). De‑energize and lock out. Use high‑temperature, appropriately rated connectors and wiring.
• Importing/using non‑listed appliances in the US can violate code and impact insurance and liability.

Practical guidelines

• Quick triage checklist:
  • Set the clock; test oven again.
  • Verify supply: 230 V at the terminal block under load; inspect for heat damage.
  • Select convection bake; check for 230 V at ring element when thermostat ON.
  • If no voltage: trace through timer relay → selector → thermostat.
  • For hob: confirm consistent spark; verify each burner sustains flame after 10–15 s hold. Measure thermocouple mV if not.
• Parts ordering:
  • Read the Art. No. on the data plate.
  • Use exploded‑view diagrams from authorized parts portals; cross‑check element wattage and geometry before ordering.
• After repair:
  • Perform insulation resistance test (>20 MΩ typical) from live parts to chassis.
  • Temperature validation: bake at 180 °C; verify ±10–15 °C stability.
  • Gas leak check with manometer/soapy solution; verify flame stability on min/max.

Possible disclaimers or additional notes

• Some sub‑variants differ (e.g., liner type, presence of tangential cooling fan, exact timer PCB). Always match by Art. No.
• Resistance values are typical; use the nameplate wattage to compute exact targets.
• If the appliance suffered a liquid spill during cleaning, allow 24–48 h dry‑out; ignition faults often clear once moisture evaporates.

Suggestions for further research

• Obtain the user/installation manual and the parts diagram for your exact Art. No.; these provide wiring diagrams, jet sizes, and torque specs.
• If chronic timer failures occur, consider adding a snubber across relay contacts (only if indicated by the OEM design) and ensure proper cooling airflow behind the fascia.
• Investigate OEM retrofit kits (e.g., updated selector switches or reinforced terminal blocks) if your serial range is affected.

Brief summary

• Mora K878AW is a 50 cm EU freestanding gas‑hob/electric‑oven cooker with a 70 L MF11 oven and electronic timer. The most common no‑heat issue is an unset/faulty timer relay; the most common uneven/no‑bake issue is a failed heating element or worn selector/thermostat. Gas issues typically trace to thermocouples or the ignition pack.
• To proceed efficiently, please share: country of installation, the unit’s Art. No., the exact symptom, and any meter readings you’ve taken. I can then give step‑by‑step diagnostics, part numbers, and test values specific to your variant.

Disclaimer: The responses provided by artificial intelligence (language model) may be inaccurate and misleading. Elektroda is not responsible for the accuracy, reliability, or completeness of the presented information. All responses should be verified by the user.