When your heat won’t turn on, it doesn’t always mean you’re in for a significant heating repair. Sometimes the fix is quick; other times, it’s your system telling you it’s time to pay attention.
Before you call for backup, walk through these troubleshooting steps to rule out the simple stuff first. This guide from Neffsville Plumbing, Heating & Cooling in Lancaster, PA, helps you stay warm and avoid a costly service visit unless it’s necessary.
Check Your Thermostat
Start with the thermostat. Make sure it’s set to “heat” and not just “auto” or “cool.” It should also be set a few degrees above your current room temperature so the system kicks in. If the screen is blank, you might just need new batteries.
Programmable or smart models may need to be reset if the schedule isn’t calling for heat. A quick manual override can test whether the system responds.
If you’ve made recent changes or installed a new thermostat, double-check the wiring connections or consult the manual to make sure it’s compatible with your unit.
Check and Replace Air Filters
Clogged air filters are one of the most common reasons a furnace stops working in winter. A dirty filter can choke airflow and cause the heat exchanger to overheat. When that happens, many systems shut down to protect internal components.
Most systems have one filter, but some may have a second filter inside the furnace cabinet near the blower. If either is clogged or collapsed, replace it. Don’t run the system without a filter, as this can damage sensitive parts inside.
Reset Your Circuit Breakers
If nothing’s running – no fan, no hum, no lights – the issue might be electrical. Go to your breaker panel and look for any switches that aren’t fully in the “on” position. If one is in the middle or flipped off, turn it all the way off and then back on again. That reset may bring your system back online.
Be sure to check near the furnace, too. Most systems have a nearby power switch that looks like a regular light switch. It’s easy to bump it by accident during storage or cleaning. Flip it back on and give the system a minute to respond.
Clear the Condensation Pan & Drain Line
High-efficiency furnaces with 90% AFUE or higher and many heat pumps produce condensation during operation. That water drains into a small pan beneath the unit and flows out through a drain line.
If the pan fills up or the line clogs, a safety switch can shut the whole system down. Take a look under your unit if the pan is full; empty it.
Check for any clogs or algae growth in the drain tube and flush it with warm water or vinegar. Once it’s clear, reset the unit and see if it starts working again.
Verify the Pilot Light or Igniter
Older gas furnaces may have a standing pilot light, while nearly all modern systems use electronic igniters. Look through the access panel for a small flame if you have an older unit.
If it’s out, you may need to relight it manually using the instructions on the unit. With electronic ignition, a worn igniter can fail to light the burners.
If yours is clicking repeatedly without igniting, or you don’t hear it at all, the igniter may need to be replaced. Never attempt to relight a gas system if you smell gas; leave and call your utility provider right away.
Inspect Your Ductwork
If your system runs but your rooms still feel cold, you could be losing heat through leaks in the ductwork. Head into the attic, crawl space, or basement and look for disconnected joints or gaps.
If you feel cold air blowing where it shouldn’t be, that’s a leak. You can temporarily seal small gaps with aluminum foil tape, not duct tape, but a pro should repair larger leaks or disconnected runs. Proper duct sealing makes a big difference in system efficiency and comfort.
Confirm the Gas Valve Is Open
If your furnace uses natural gas or propane and won’t produce heat, the gas supply may be interrupted. One possible cause is a closed valve on the incoming line. If the handle is perpendicular to the pipe, gas flow is likely off.
If it’s aligned with the pipe, gas should be flowing. However, if you suspect the valve is shut, stuck, or difficult to move, do not attempt to turn it. Gas lines can corrode or become damaged over time.
Leave the system off and contact a licensed HVAC technician to assess the issue safely.
Assess the Outdoor Exhaust Vent
Modern furnaces vent combustion gases through an exterior wall using a plastic exhaust pipe. If that pipe gets blocked by snow, leaves, or nests, your system will shut down to prevent dangerous buildup.
Walk around the outside of your home and locate the vent. Make sure it’s clear and that air can flow freely. In cold climates, this vent can freeze over or become buried in snowdrifts, especially after a storm. Keep it clean throughout the season to avoid repeated shutdowns.
Inspect Outdoor Heat Pump Components if applicable
If you use a heat pump, your system depends on outdoor components just as much as indoor ones. Snow, ice, or leaves can block airflow and reduce performance. Check the unit’s sides and top for buildup.
If ice has formed on the coils or casing, your defrost cycle may not be working properly. Don’t chip at the ice; it’s easy to damage the fins. Turn off the unit and call for service if it doesn’t thaw on its own after clearing the airflow path.
When to Call in a Pro
You don’t need to solve every heating issue yourself. If you’ve walked through all the steps above and the system still won’t run, or if you’re not comfortable inspecting electrical or gas components, don’t push it.
Neffsville Plumbing, Heating & Cooling is here to help when your heater leaves you in the cold. Our licensed technicians can diagnose hidden problems, replace faulty parts, and get your home warm again fast.
Schedule your heating repair today to ensure your system runs reliably.
