Rinnai Furnace 18 Error Code — Meaning & Repair Cost (2026)
Thermocouple output error. Below: the most likely causes, and what the matching repair costs — Estimated national ranges with a metro localizer. Reviewed July 2026.
What 18 means
Thermocouple output error.
Likely causes, most common first
- Low gas supply, wrong gas type, or a sensor fault
Base: 1 published national repair-cost guide (retrieved 2026-07) · full source registry on the methodology page · Code meaning & causes · Reviewed July 2026
What it usually costs to fix Estimated
18 on a Rinnai furnace resolves to the gas furnace pilot light / thermocouple won't stay lit problem. We don't yet publish a verified parts factor for Rinnai, so the ranges below use the mainstream baseline.
$150–$700 national estimate to fix the fault behind 18. Enter a ZIP to localize.
| Most common repair | Typical total | DIY? |
|---|---|---|
| Thermocouple cleaning/replacement | $150–$300 | DIY possible |
| Pilot assembly clean/replace (standing-pilot models) | $150–$350 | Pro recommended |
| Gas valve replacement (standing-pilot, root cause of last resort) | $300–$700 | Pro recommended |
Plus a typical service-call / diagnostic fee of $75–$150, often credited toward the repair.
Pick a quality tier for a class-typical estimate, or a specific brand to override it (brand adjusts the parts portion only). Enter a ZIP or Canadian postal code to localize to your metro's labor costs. Everything updates without a page reload; no data leaves your browser except the shard lookup.
Base: 2 published national repair-cost guides (retrieved 2026-07) · full source registry on the methodology page · National base range (BLS OEWS May 2025 + BEA RPP 2024) · Reviewed July 2026 · Estimated
Codes are universal — your location changes the repair price, never the code's meaning. See the methodology for the exact localization formula and sources.
Reviewed by a Red Seal–certified appliance technician who also holds a Technical Safety BC gas ticket (Gas-C) and an ODS/halocarbon refrigerant ticket (CFC/HCFC/HFC).