Late afternoon in Bunker Hill Village, our phone lit up with a nervous homeowner: “The oven won’t ignite — we have guests at 7.”
They owned a Thermador Pro Harmony range and assumed the fix was simple: swap an oven igniter, close the panel, and dinner is saved.
Our technician arrived thinking the same. However, after a careful test, reality pushed back.

Not one, but all four oven igniters stayed silent. The control relays clicked on cue, yet voltage never reached the igniters.
On older designs we often see an inline thermal cutoff or a damaged high-temp fuse. But modern Thermador platforms consolidate protections and ignition logic into multi-board control architecture — fewer “cheap fuses,” more intelligent boards.
Pulling from the official service literature, our tech mapped the ignition circuit, verified the harness and neutral, and isolated the failure to the ignition control section on the main logic board.
That’s why we treat Thermador like a supercar: precise tests first, parts second. You wouldn’t do an oil change on a Lamborghini in the driveway; your Thermador deserves the same respect.

If your premium range misbehaves — clicks without lighting, won’t heat, runs its fans at odd times, or throws a code — skip the guesswork.
We bring manufacturer-level diagnostics, clean workmanship, and local accountability. Book at
HomeFix Appliance Repair, call
346-489-7171
Also, Thermador’s official Owner Resources (useful user-level manuals) live here:
thermador.com/us/support/owner-resources.

Range Repair Service We Provide (What Really Happened in Bunker Hill)

We approached the failure like Thermador intends: verify input power, confirm correct gas supply, then isolate ignition.
First, we reseated burner caps and grates (even on an oven call, cooktop mis-seating can create false feedback). Next, we inspected the oven harness, checked for grounded electrodes, and monitored the control board as relays toggled — we heard the clicks but measured no output to the igniters.
Because newer Thermador platforms manage ignition via the main logic/control assembly and dedicated spark modules, loss of drive to all oven igniters points away from four simultaneous igniter failures and toward the upstream control logic.
Our tech used the manufacturer’s step-by-step diagnostic structure to identify the exact board channel at fault and advised a professional repair path (without listing part numbers here — safety first).

Importantly, modern Thermador designs use multiple sub-systems: standard spark modules for most burners, green-label XLO spark modules for extra-low cycling burners, main logic/relay boards for ovens, cooling fans, LED indicators, thermostats, probes, regulators, and optional Home Connect modules.
Each sub-system has service-level tests and known symptoms (for example, clicking continues after flame because the electrode never reports “flame present”).

Most Common Thermador Range Problems We Fix (and How Pros Diagnose Them)

Below you’ll find a comprehensive, real-world catalog of issues we regularly see on Thermador Pro Harmony / Pro Grand ranges in Houston.
We included why they happen, how a pro confirms them, and what makes Thermador’s design unique. Skipping DIY details protects your appliance — and your kitchen.

1) Igniter clicks but no flame (single burner)

What you see: Audible sparking, no ignition on a specific burner.
Likely causes: Wet or dirty electrode from recent cleaning, mis-seated STAR burner cap, clogged ports, or a cracked ceramic insulator.
Pro checks: Dry and clean the electrode; confirm correct cap placement and port cleanliness; verify ground and harness integrity; ensure flame lights within ~4 seconds at each STAR burner.
Mis-placed caps can cause uneven flame, lifting, or gas odor — Thermador explicitly warns about this.

2) All cooktop burners won’t ignite

What you see: No spark anywhere; or clicking stops abruptly across all burners.
Likely causes: No line power, tripped breaker, failed spark module (white label standard module), or disconnected/shorted common ground.
Pro checks: Verify 120 VAC, polarity, and ground; inspect spark module connectors; sub in a known-good standard module; confirm that XLO (green label) modules still cycle correctly on extra-low burners.

3) XLO (Extra-Low) burners surge or won’t hold a simmer

What you see: Left-side XLO burners cycle too aggressively or stall.
Likely causes: XLO IRIS module fault (green label), solenoid valve wiring, or incorrect valve calibration.
Pro checks: Inspect IRIS module seating on valve body; verify solenoid harness; validate cycling behavior between SIM and XLO ranges per design.

4) Constant clicking after flame is lit

What you see: Burner lights, but the igniter keeps clicking.
Likely causes: Ground feedback due to a wet electrode, cracked porcelain, or short along the electrode lead. The control doesn’t “see” flame and continues to spark.
Pro checks: Dry the area; inspect electrode tip and insulator; check harness insulation and routing; verify that continuous clicking stops when a known-good electrode is installed.

5) Oven won’t heat / underheats / shuts off early

What you see: Long preheat, never reaching setpoint, or cycling off too soon.
Likely causes: Temperature sensor drift, bake/broil relay failure on the main board, hidden bake element open, or cooling airflow issues overheating the electronics.
Pro checks: Measure sensor resistance vs. spec; test voltage to hidden bake element (Thermador hides it under the floor, so visual checks mislead); watch relay commands from the control. If the unit overheats the electronics compartment, the bake relay may drop out to protect the board.

6) Fault Code 43 — “Cooling Fan Not Operating”

What you see: Code 43 after a cycle, especially with a decorative backsplash or after service.
Likely causes: Back-splash vents not aligned with the cooling fan inlets, or the sail switch mounted at a downward angle so it never returns to “open” at shutdown.
Pro checks: Verify airflow path behind the range; reposition sail switch plate parallel to the fan housing; drill a new mounting hole if required (per BSH instructions). We run the oven several times to confirm proper switch action and steady airflow.

7) Oven lights work but no bake/broil and you hear relays click

What you see: Control lights and clicks, but zero heat.
Likely causes: Open line/neutral to element circuit, failed high-temp cutout (on variants that still use one), or a failed output channel on the main relay board.
Pro checks: Confirm supply at board output while relay is engaged; trace neutral continuity; check whether the specific model includes a thermal cutout near the terminal box. (Thermador platforms vary by FD date and series.)

8) Uneven or lifting cooktop flame (orange tips, noisy lift-off)

What you see: Flame “dances,” shows yellow tips, or lifts off cap edges.
Likely causes: Wrong gas type/regulator setting, cap mis-placement, drafts, or heavy hood flow.
Pro checks: Verify regulator direction and gas type; confirm 7″ WC for NG or correct LP config; reseat caps; clean ports; evaluate hood airflow and make-up air. Thermador describes normal blue flames (NG) and acceptable LP yellow tips after warm-up; we rely on these OEM visuals during adjustment.

9) Grill or griddle runs hot, cold, or trips safety

What you see: Uneven sear, thermostats tripping, or module shuts down early.
Likely causes: Failing safety thermostats, loose harnesses under the module, or insulation shift.
Pro checks: Access module, verify thermostat mounting and wiring, check element continuity and harness routing; replace brittle harnesses and re-secure insulation panels to restore proper thermal behavior.

10) Cooling fan runs loud or forever

What you see: Fan noise that grows over months; or fan continues long after shut-off.
Likely causes: Bearing wear, debris contacting blades, or fan running by design to cool the control compartment. If it never stops, look for a sensor/switch or board logic fault.
Pro checks: Inspect fan wheel/bearings; confirm that fan behavior matches operating mode; rule out Code 43 airflow/switch issues; validate that board shuts the fan off once temps fall.

11) Door won’t soft-close / alignment off / slams

What you see: Lost soft-close action, misalignment, or a slam at final inches.
Likely causes: Damper and carriage pin out of sync or dry; hinge not seated in receivers; heat-aged grease.
Pro checks: Realign door on receivers, reset tension in the soft-close device, and inspect the damper stop and pin. Proper re-tensioning restores the smooth “pull-in” Thermador describes.

12) Meat probe errors (single-point vs multi-point)

What you see: Probe won’t detect, reads erratically, or ends a cook prematurely.
Likely causes: Wrong probe type for the socket (2-pole vs 3-pole), damaged connector, or NTC drift.
Pro checks: Identify connector type, test continuity, inspect harness path, and validate temperature change on warm water test. Multipoint probes read more reliably if placement isn’t ideal.

13) Oven light / “door open” logic issues

What you see: Light stuck off/on, or bake cycle aborts because the control “thinks” the door is open.
Likely causes: Failing door switch or fatigued wiring in the hinge area.
Pro checks: Meter the switch, inspect strain-relief and flex points, and verify control response when switch is manually actuated.

14) Gas odor or inconsistent flame height across burners

What you see: Smell near the manifold or at specific burners; one star burns taller/shorter.
Likely causes: Loose jet holder, regulator leak, damaged O-ring on XLO solenoid, or venturi blockage.
Pro checks: Bubble test on manifold/regulator fittings; verify jet holder seating and venturi torque by model; on XLO, examine the large hex union and O-ring integrity; always re-check with a gas detector after reassembly.

15) Control panel buttons/indicators unreliable

What you see: LEDs flicker, some controls lag, temperature gauge doesn’t reflect setpoint changes.
Likely causes: Aging connectors at the back of the control panel, failing temperature gauge assembly (note: it displays set temperature, not cavity temp), or minor corrosion in the ribbon cables.
Pro checks: Remove panel per OEM order of operations; re-seat harnesses; test gauge function and replace if non-responsive.

16) Home Connect / communication errors

What you see: App disconnects, sporadic messages, or failed pairing.
Likely causes: Faulty Home Connect module, wiring to the module, or firmware anomalies.
Pro checks: Access the HC module under the maintop; reseat harness; replace the module if it fails checks; then re-test connectivity.

17) After cleaning: multiple burners won’t light

What you see: Several electrodes wet at once; unit clicks repeatedly.
Likely causes: Moisture around electrode wells or down venturi tubes.
Pro checks: Dry time with low heat and ventilation; inspect for liquid in wire wells; clean carbon at tips; confirm re-grounding after reassembly. Thermador notes electrodes should ignite within ~4 seconds once conditions normalize.

18) Post-storm: dead oven but cooktop works

What you see: Power surge took out a control channel; cooktop igniters still click.
Likely causes: Relay output driver damage on main board; failed low-voltage supply to oven circuit.
Pro checks: Meter low-voltage rails on the control, confirm bake/broil outputs under command, and evaluate cooling fan path — overheated electronics after a surge can fail later under load.

19) Warm drawer/aux features unresponsive (48″/60″ platforms)

What you see: Auxiliary zones dead or intermittent.
Likely causes: Harness loosened during prior service, auxiliary thermostat faults, or drawer switch issues.
Pro checks: Follow OEM disassembly to reach the auxiliary harness, test thermostats/switching, and verify full operation before re-installing panels.

20) “Everything died after a relocation or remodel”

What you see: Unit powered, but many subsystems misbehave after moving the range, changing countertops, or adding a tall backsplash.
Likely causes: Pinched harness behind the unit, misrouted ground, airflow blocked by a new backsplash, or different hood creating draft problems.
Pro checks: Pull unit out and inspect harness/grounds; confirm correct vent alignment behind cooling fans; test bake cycles repeatedly to verify correct sail-switch action and temperature stabilization.

Why We Don’t Post Part Numbers (and Why You Win When We Don’t)

Thermador engineered Pro Harmony/Pro Grand with modular electronics and tight thermal management. The same symptom can trace to different modules depending on FD date, feature set (grill, griddle, steam), and burner configuration.
Posting parts turns “research” into risky DIY. Instead, we publish transparent diagnostics in plain English, then do the precise repair on site with the right tools and torque — exactly how the service documentation expects.

Need Thermador Range Repair in Houston?

We serve Bunker Hill Village 77024, Memorial, Spring Branch, and all nearby Houston neighborhoods.
Schedule help at appliancerepair-homefix.com, call
346-489-7171
For user-level manuals and care tips straight from the manufacturer, visit Thermador’s
Owner Resources.

FAQ — Thermador Range Issues