Won't start

Abnormal noises are highly diagnostic: 'Thumping' = loose tumbler baffle, worn/misaligned rear rollers, out-of-round drum or high weld seam. 'Ticking' = loose wire harness or object caught in blower wheel. 'Scraping' = front or rear bulkhead felt seal out of position or worn front bearings. 'Roaring' = blower wheel rubbing on housing or bad motor bearings. 'Popping/squealing' = sticky or frayed belt. Whistling = check door seal condition.

Gas ignition failures present in exactly 3 distinct patterns: (1) Igniter does not glow — check flame sensor, igniter, booster coil, motor switch, wiring. (2) Igniter glows but no ignition — check secondary coil, holding coil, wire harness, stuck flame sensor. (3) Gas ignites but flame goes out — check radiant sensor contacts, weak gas valve coil, hi-limit, poor venting, bad drum seals. Each pattern points to different root causes.

Different noise types diagnose different components: 'Thumping' = loose tumbler baffle, worn/misaligned rear rollers, out-of-round tumbler or high weld seam. 'Ticking' = loose wire harness or object in blower wheel area. 'Scraping' = front/rear bulkhead felt seal out of position or worn front bearings. 'Roaring' = blower wheel rubbing on housing or bad motor bearings. 'Popping/Squealing' = sticky or frayed belt.

When the power does not work but voltage and terminal block are confirmed good, check the flat wire connecting the main and sub PCBs. A damaged or poorly seated flat wire is a common cause of 'no power' and 'no display' symptoms that may be misdiagnosed as a failed PCB. The diagnostic flowchart specifically calls out checking this flat wire before replacing any PCB.