Heater Not Working? Quick Checks Before You Call for Service

When your heater isn’t performing, these are the first things to check — in order — before calling for service. Our technicians walk homeowners through these over the phone every day.

1. Check the Thermostat

Verify it’s set to HEAT mode, the set temperature is above the current room temperature, and the fan is set to AUTO. Check that the batteries aren’t dead (if applicable) and that the display is on. A thermostat with a blank screen means no signal is reaching your heating system.

2. Check the Air Filter

A clogged filter is the most common preventable cause of heating problems. If the filter is visibly dirty, replace it. A severely restricted filter causes the furnace to overheat and shut down on the high-limit safety switch.

3. Check the Breaker

Your heating system has a dedicated breaker (or two — one for the air handler/furnace, one for the heat pump outdoor unit). If either is tripped, reset it once. If it trips again immediately, do not keep resetting — call a technician.

4. Check the Gas Supply (Gas Furnaces)

Verify the gas valve on the supply pipe near the furnace is open (handle parallel to the pipe). If you have other gas appliances, check if they’re working to confirm gas supply to the house.

5. Check the Outdoor Unit (Heat Pumps)

If you have a heat pump, check the outdoor unit. Is the fan running? Is there ice buildup on the coils? Light frost during winter operation is normal — the system has a defrost cycle to handle it. Heavy ice buildup (thick ice coating the entire unit) is not normal and indicates a defrost cycle failure or low refrigerant.

Do not try to chip ice off the unit. Call for service.

6. Check Your Vents

Make sure all supply and return vents are open and not blocked by furniture, rugs, or curtains. Blocked returns cause pressure imbalances that reduce system performance and can trigger safety shutdowns.

When These Checks Don’t Fix It

If you’ve gone through all six steps and the system still isn’t heating properly, the issue is beyond DIY troubleshooting. Common professional-level repairs include: igniter replacement, flame sensor cleaning, capacitor replacement, refrigerant recharge, control board repair, or blower motor service.

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Call Waldrop Plumbing Air Electric at (864) 536-0887. We offer 24/7 emergency heating service.

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