Furnace Diagnostic

When Your Furnace Won't Heat Right

A furnace that short-cycles, throws an ignition lockout, or heats one room but not another is telling you a specific component is failing — not that it's just old. Our heating diagnostic isolates the actual failure so you're not guessing (or replacing parts that were fine) to solve a problem.

What Our Furnace Diagnostic Actually Checks

Heat exchanger integrity. A cracked heat exchanger is the one furnace failure we can't repair — it's a safety condemn. We inspect visually with a camera scope, check flame pattern for roll-out, and look for carbon monoxide levels above and around the return plenum. If the exchanger is compromised, we shut the unit down and explain the replacement path.

Gas pressure — inlet and manifold. A furnace running on wrong gas pressure will short-cycle, throw limit lockouts, or run inefficient. We put a manometer on the inlet and manifold ports and verify against the nameplate spec. Under-fired and over-fired both cause damage — under-fired often gets misdiagnosed as a "bad thermostat."

Flame sensor, hot surface igniter, or spark igniter. On a 90%+ furnace, a dirty flame sensor causes about 40% of the "won't light" calls we see. We clean, verify microamp reading, and check the ignition control board's response. On older 80% units with a spark igniter, we check spark quality and gap.

Inducer, pressure switch, and venting. The inducer motor pulls combustion air; the pressure switch verifies it's actually pulling. A blocked or slightly cracked vent pipe will let the pressure switch open intermittently — you'll see a lockout code but no obvious external problem. We check both.

High limit, roll-out switch, and control board. A furnace that repeatedly trips the high-limit is telling you it can't move enough air across the heat exchanger — usually a filter or duct restriction, sometimes a failing blower. We diagnose the root cause, not just the symptom.

What You Get

A clear explanation of what's failing, whether it's repair-worthy or replace-worthy, and the cost trade-offs of each path. If it's a safety issue, we tell you straight. Book a furnace diagnostic today.