Direct answer
For the LG WCEP6423 combination wall oven, mode, temperature, door state, power/gas supply and element/burner operation should be separated. First, select Bake at a moderate temperature and observe ignition or element behavior.
What this covers
- LG WCEP6423 combination wall oven (WCEP6423F)
- LG combination wall oven — no cooktop at all; every burner symptom is out of scope for this unit.
- The specific fault this record addresses: oven will not heat or preheat
What it does not cover
- ×The same symptom on a different LG product line, which has its own record and its own cited source
- ×An on-screen error code whose meaning has not been checked against this exact model's manual
- ×Live electrical, gas, sealed-system, internal battery-cell or structural repair — a technician boundary, not a self-service step
Differential
What actually causes this, and how to tell them apart
These are ordered by how often each one is the answer, not by how easy it is to try. The point of the middle column is that two causes producing the same headline symptom rarely produce the same detail — that detail is what tells you which one you have before you change anything.
- 1
The bake or broil element has failed
What separates it No heat, no error code, and — if visible — no visual glow from the element that should be present within the first minute of a Bake call.
How to confirm A visibly intact element that never glows during a call for heat, with confirmed household power present, points to the element itself or its control relay.
- 2
No household power is reaching the oven's control or element circuit
What separates it Complete darkness on the display as well as no heat — this is a different symptom from a lit, functioning display that simply produces no heat.
How to confirm Check both poles of the range's breaker before assuming an internal fault; see the no-power symptom for the full path.
- 3
A Sabbath mode or a control lockout is suppressing normal operation
What separates it The display behaves unusually — showing a specific icon, refusing certain button combinations, or holding a fixed temperature regardless of setting.
How to confirm Check the manual for the exact icon and the documented sequence to exit that mode; it is not the same on every brand.
- 4
The oven safety thermostat or control board has failed
What separates it Confirmed power, confirmed intact element or a normally-glowing igniter, and still no heat — this is the conclusion only once supply and the primary heat-producing part are ruled out.
How to confirm This is a technician diagnosis reached after eliminating the more common causes above.
Before you touch a setting
Record this first — changing settings destroys the evidence
Every item below stops existing the moment a reset, re-pair or settings change is made. Written down first, they are what separates the causes above; recovered afterwards, they are guesswork.
- Whether this is a gas or electric oven — the igniter-and-valve sequence and the resistance-element behavior are different failure paths with different tells.
- Whether the display is fully dark (a power problem) or lit and responsive but simply not heating (a heat-path problem).
- For gas ovens: how long the igniter glows before the control gives up, if it glows at all.
- Any special mode icon showing on the display.
Confirm household power is present at both breaker poles
ReversibleRule out a power problem before diagnosing the heat path itself.
Select Bake at a moderate temperature and observe the first minute
ReversibleFor gas, time the igniter glow before ignition; for electric, watch for the element beginning to glow.
Check for and exit any Sabbath mode or control lockout
ReversibleUse the manual's exact sequence for this model.
Arrange service for a confirmed failed igniter, element, valve or control board
ReversibleThese are standard replacement parts but not typically safe DIY repairs given gas or high-voltage exposure.
Measure a full preheat cycle after correction
ReversibleConfirms the fix reaches and holds temperature, not just that heat is present momentarily.
Model-specific
What is true of this model and not of its siblings
Generic advice for the product line fails here. Each item below is a property of this specific model family that changes which of the steps above apply to you.
- Model scope
- WCEP6423F. LG combination wall oven — no cooktop at all; every burner symptom is out of scope for this unit.
- Type — combination WALL OVEN (no cooktop)
- A built-in combination WALL OVEN — an oven-only appliance with no cooktop or burners, so cooktop/burner symptoms do not apply. 'Combination' means it pairs a full oven with a second cavity (often a microwave or speed oven), so a 'not heating' can be the microwave/speed cavity versus the main oven element — identify which cavity.
- Oven — electric
- Electric oven with convection and Air Fry on most builds; no-heat on the main oven is the element or control. Being built-in, it runs on a dedicated circuit — a completely dead unit is often that breaker.
- Features
- ProBake convection, ThinQ Wi-Fi on smart builds. Self-clean locks the door with some smoke/smell normal on the high-heat cycle.
- Symptom boundary
- This record covers LG WCEP6423 combination wall oven when it oven will not heat or preheat. A different symptom on the same hardware, or this symptom on a different LG product line, has its own record with its own causes and its own cited source.
Stop boundary
When this stops being a self-service repair
Continuing past any one of these costs more than the repair saves — in safety, in warranty, or in evidence a technician needs.
- !Gas odor at any point: stop, do not operate any switch, ventilate, leave and call the gas utility or emergency services from outside.
- !Repeated breaker trips, arcing, or a smell of burning insulation mean stop and call for service rather than continuing to test.
Evidence ledger
Sources behind this answer
Visible sources support the visible claims. Home Product Support records the publisher, the fact used and the review date; community reports can suggest an issue but do not become a published fact on their own.
Where the manufacturer's article stops. LG publishes this as "Oven Not Heating- Gas and Electric Ranges". Oven that will not heat or preheat, covering both gas and electric ranges. What that article does not carry is the model boundary — it is written for a product line, and WCEP6423F is the scope applied here. Where a control label, terminal, indicator pattern or reset sequence differs on your unit, the manual for that exact model is the authority, not this page and not the article.
Exact questions
Common follow-ups
One cavity of my LG WCEP6423 heats but the other doesn't.+
This is a combination wall oven with two cavities (typically a main oven and a microwave/speed oven), which work differently — so identify which cavity has the problem. The main oven uses bake/broil/convection elements; the upper microwave or speed-oven cavity uses microwave energy or a smaller element. A fault in one does not affect the other, and there is no cooktop on this unit, so burner troubleshooting does not apply.
My gas oven's igniter glows but nothing lights.+
An igniter has to reach a specific resistance to trip the gas safety valve open — a weakening igniter can glow, sometimes for a long time, without ever reaching that point. Time how long it glows before giving up; a normal ignition happens within seconds, so a long glow with no ignition points at the igniter.
My electric oven shows no error but never gets hot.+
Check whether the bake element visibly glows within the first minute of a Bake call, with power confirmed present. An element that stays completely dark despite a call for heat points to the element or its control relay, not the thermostat.
Does this answer apply to every LG model?+
No. It is scoped to WCEP6423F. LG combination wall oven — no cooktop at all; every burner symptom is out of scope for this unit.
What should I record before troubleshooting oven not heating or preheat?+
Record the complete model identifier, exact message or indicator, software/firmware where visible, the operating stage and what still works.
Why is a factory reset not the first step?+
A reset can erase accounts, networks, maps, schedules or preferences without distinguishing oven not heating, preheat. The ordered checks preserve that evidence.
When should I stop and use qualified service?+
Stop for gas odor, arcing, smoke, runaway heat or repeated breaker trips.
Answer for the exact device and software version shown above.