FURNACE PROBLEM · DIAGNOSIS GUIDE
Five common reasons a furnace runs but doesn't produce heat — and when to stop troubleshooting and call us.
If your home is below 50°F and the furnace won't restart after basic checks (thermostat, filter, breaker, gas valve), treat it as an emergency. Frozen pipes are an expensive way to find out your heating system needs work.
Verify it's set to HEAT, the temperature is above room temp, and the batteries (if any) work. Some thermostats need a hold-button to override schedules.
Many furnaces have a service switch (looks like a light switch) on or near the unit. Check it's ON. Check the breaker in your panel too.
If you have a gas furnace, verify the gas valve at the unit is open. If you have natural gas service, verify your gas service is on (check other gas appliances). If propane, check the tank level.
A heavily clogged filter can trigger the limit switch and shut the burner down to prevent overheating. Replace the filter.
Older furnaces have a standing pilot that can go out. Newer ones have an electronic igniter that can fail. Both are common failure points.
If your home is below 50°F and the furnace won't restart after basic checks, treat it as an emergency. Frozen pipes are an expensive way to find out your heating system needs work.
We answer 24/7 for genuine furnace emergencies. A real licensed technician picks up the phone — not voicemail. Call (973) 948-0680.
$150-$425.
$150-$400.
$300-$700.
$400-$700.
$600-$1,800 repair, but cracked heat exchangers are usually a replacement decision.
“Furnace died on the coldest night of January. They were at the house in 45 minutes, had the part on the truck, and we were warm again in two hours.”
Susan L. · Hackettstown, NJ
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98 Morris Turnpike, Newton NJ · NJ HVACR Lic #19HC00108700 · Since 1999
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