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The ticket arrived with a pre-written diagnosis: “the range potentiometer needs to be replaced.” The customer, in the Bow Valley mountain hamlet of Lac des Arcs between Canmore and Exshaw, had already concluded which part had failed on their Thermador Pro Grand 36-inch gas range. TechVill technician Hardeep verified that conclusion on site before touching a single component — and the actual fault turned out to be something else entirely.
What the customer reported
The customer arrived with a self-diagnosis — the temperature-control potentiometer. That assumption is a reasonable starting point: when an oven misbehaves, the control electronics are an obvious suspect. But a pre-diagnosis, whether it comes from an online search or earlier troubleshooting, is the start of the diagnostic conversation, not its conclusion.
On a Thermador Pro Grand PRG364GDH/11 — flagship pro-style cooking equipment — acting on the wrong part has a real cost. Replace a potentiometer that was never failing, and the customer pays for a part they didn’t need while the actual fault stays unaddressed, forcing a second visit. Verifying the diagnosis on site is the discipline that prevents both outcomes.
What the diagnostic showed
Hardeep ran symptom-based verification on the oven and found a different root cause. The potentiometer governs temperature setting and display — it had nothing to do with the failure. The real symptom was that the bake ignitor was not initiating the burner flame.
On a gas oven, the bake ignitor glows hot when the oven calls for heat and draws enough current to signal the safety gas valve to open. Gas then ignites against the still-glowing ignitor and the burner flame establishes. When the ignitor ages out or develops microcracks, its current draw drops below the threshold the valve needs — so the valve stays closed, no gas reaches the burner, and the oven never heats. That is a completely different fault category from a potentiometer issue, which would never stop flame initiation. The customer’s part was working; the ignitor was not.
The repair
Based on the diagnostic findings, Hardeep replaced the bake ignitor in a single visit. Before installing a part, he walked the customer through the options.
Component replaced:
- Bake ignitor (Electrolux-compatible service part) – glows hot to draw the current that signals the safety gas valve to open, so the oven burner can light and hold its flame
The customer was offered an Electrolux-compatible ignitor at a lower cost than the OEM Thermador part, carrying the same 90-day labour warranty, and chose to proceed with it. This was the customer’s informed decision, recorded on the work order — a transparent cost option, not a substitution made on their behalf. The compatible part fits the Thermador ignitor’s mechanical and electrical specifications, and the warranty on the repair is identical to what an OEM repair would carry, so the cost savings came with no reduction in repair protection.
Post-repair verification:
After installation, the range was tested in bake mode. The new ignitor was observed glowing properly, the gas burner ignited normally, and the oven reached preheat temperature and continued cycling correctly through an extended test period with no further issues. Because this is a gas appliance, the work order also documents an explicit safety check — no gas leak, electrical fault, or damage at the replaced component. The customer was present and verified operation firsthand.
Why the difference matters
The total came to $510 CAD plus 5% GST, $535.50 CAD, settled in full at the visit — diagnostic, customer decision, repair, and an eight-step functional and safety verification, all in one trip. Had the work proceeded on the customer’s original assumption, the bill would have covered a potentiometer that was never broken, the oven still wouldn’t heat, and a return visit would have followed.
That is the value of verifying a fault on site rather than acting on a stated assumption. Lac des Arcs sits in the Bow Valley mountain corridor, where a service call means more than an hour of travel each way from Calgary — the kind of trip few shops make and one where a second visit is especially costly. TechVill repairs Thermador appliances across the Calgary and Bow Valley area, with technicians who arrive with the test equipment to confirm the actual fault before any part goes in.
Book online to schedule a Thermador gas range diagnostic with our team.
