Why Is My Heat Not Working? 8 Things to Check Before Calling an HVAC Tech
Before you pay for a service call, run through this 8-step troubleshooting checklist. You might fix it yourself in 5 minutes — and we'll tell you exactly how.
We get it — a no-heat call costs money. Before you pick up the phone, run through these 8 quick checks. Honestly, about a third of the time customers fix it themselves, and we'd rather help you avoid an unnecessary bill than charge you for a flipped breaker.
1. Check the Thermostat
Make sure it's set to HEAT (not COOL or OFF), and that the setpoint is at least 3°F above the current room temperature. Replace the batteries if it's not hardwired — dead thermostat batteries are the #1 'phantom' failure we see.
2. Check the Furnace Switch
There's usually a wall switch that looks like a light switch near or on the furnace. It's labeled, but in old houses it might just be a random switch in the basement. If it's off, flip it on.
3. Check the Breaker
Find the breaker labeled FURNACE or HEAT and flip it fully off, then back on. Don't just nudge it — fully off, then fully on.
4. Check the Air Filter
A clogged filter starves the furnace and trips a safety. If yours is gray or you can't see through it against a light, replace it.
5. Check the Front Panel
Most furnaces won't fire if the front panel isn't fully seated. Push it on firmly until it clicks.
6. Check the Condensate Drain (High-Efficiency Only)
If your furnace has PVC venting, it's a high-efficiency unit with a condensate pump or drain line. If the line is clogged or the pump failed, a safety switch shuts the furnace off. Look for water around the base of the unit.
7. Check for a Blinking LED
Look through the little window on the furnace. A blinking LED is the furnace telling you what's wrong — Google your model + the blink code and you'll often find a quick fix.
8. Check for a Tripped Pilot or Ignition Lockout
Newer furnaces will lock out after 3 failed ignition attempts. Turn the thermostat down for a minute, then back up to trigger a reset.
Still No Heat?
If you've worked through all 8 and you're still cold, give us a call at 856-816-4822. We run 24/7, and we'll get someone out as fast as humanly possible — usually same day.
Frequently asked
Why does my furnace turn on and then shut off after a minute?+
Classic 'short cycling.' Almost always a dirty filter, a flame sensor that needs cleaning, or a failing limit switch. The first one's free to fix; the other two are easy service calls.
What's the most common cause of a no-heat call?+
Thermostat batteries and dirty filters together account for nearly 40% of the no-heat calls we get on the coldest week of the year.
How fast can S&M come out for emergency heat?+
We run 24/7. In Mount Ephraim and surrounding towns we typically get there within 1–3 hours, even on holidays.
Call Scott and the S&M crew — free, honest advice from real licensed techs.
856-816-4822