What fails at the first start-up after summer
A Sacramento furnace sits idle from spring to late fall and then gets switched on all at once. Most first-of-the-season no-heat calls are not worn-out furnaces — they are the predictable consequences of eight months of standing still.
Flame sensors top the list. A film builds on the sensing rod, the board cannot confirm a flame, and the furnace lights and shuts down seconds later, again and again.
Hot-surface igniters are next. They degrade with every cycle and drift out of resistance range before they finally crack, so the furnace either takes several attempts to light or never lights at all.
Dust burning off the burners and heat exchanger causes the smell people notice on the first cold night. A faint smell for a few minutes is normal. A persistent burning-plastic or hot-metal smell is not — shut the system off and call.
Blocked condensate drains on high-efficiency furnaces trip the pressure switch and prevent the burner from firing at all, which looks identical to a dead furnace from the thermostat.
Seized or noisy inducer and blower motors announce themselves at start-up after months of idle bearings, usually as a squeal, a hum with no rotation, or a unit that trips the breaker.
And filters left in since spring starve airflow, push temperature rise above the rated range, and trip the high-limit switch — a furnace that heats briefly and then shuts itself off over and over.
Nearly all of it is catchable ahead of time. See our furnace tune-up and heating maintenance page for what a pre-season visit covers, and call (916) 477-3735 if the system is already down.