In This Guide
AC Stopped Cooling: What to Check First
Look at the air filter. A clogged filter restricts airflow and is the single most common reason an AC seems to "stop working" when it's actually just struggling to push air through.
Confirm the thermostat is set to "cool" and the target temperature is below the current room temperature, not accidentally switched to "heat" or "off."
Check your breaker panel for a tripped breaker on the AC circuit — outdoor condenser units are especially prone to tripping during high-demand periods.
Look at the outdoor condenser unit for visible ice buildup or debris blocking airflow. If you see ice, turn the system off — running it iced-over can cause further damage.
Furnace Won't Heat: What to Check First
Confirm the thermostat is set to "heat" with a target temperature above the current room temperature.
Check that the furnace's power switch (often a light-switch-style toggle near the unit) is in the "on" position — it's easy to accidentally bump.
Check your breaker panel and, for gas furnaces, confirm the gas supply valve is open.
Replace the air filter if it hasn't been changed recently — a clogged filter can cause a furnace to overheat and shut itself off as a safety measure.
Warning Signs That Mean Stop and Call a Pro
- Ice on the indoor coil or outdoor unit: Usually means restricted airflow or low refrigerant — continuing to run the system risks further damage.
- A burning smell from vents: Could indicate dust burning off after a long idle period (often harmless and brief) or, if persistent, an electrical or component issue worth having checked.
- Strange noises: Grinding, squealing, or banging sounds usually point to a mechanical issue inside the unit that needs professional diagnosis.
- Water pooling near the indoor unit: Often a clogged condensate drain line, which can cause water damage if left unaddressed.
- Repeated breaker trips on the HVAC circuit: Similar to electrical issues elsewhere in the home, repeated tripping signals an underlying fault rather than a one-time overload.
Checked the basics and still no luck? Get a licensed HVAC technician dispatched to your home now.
📞 Call +1 (858) 477-5941Seasonal Pressure: Heatwaves and Cold Snaps
HVAC systems fail disproportionately during extreme weather — not coincidentally, but because that's exactly when they're working hardest. A few things to know:
- During heatwaves: AC systems run nearly continuously, which is when worn components and low refrigerant levels tend to finally cause a breakdown. Same-day dispatch becomes harder to get the longer you wait once a heat advisory is in effect.
- During cold snaps: Furnaces that haven't been used much all year are suddenly running constantly, which is when ignition issues and worn parts surface.
- Booking ahead matters: If you know a heatwave or cold snap is coming and your system has been acting up, it's worth getting it checked before the extreme weather hits rather than after.
Safe DIY Checks vs. Calling a Technician
Reasonable to Check Yourself
- Replacing or checking the air filter
- Confirming thermostat settings and batteries
- Checking the breaker panel for a tripped breaker
- Clearing debris away from an outdoor condenser unit
Call an HVAC Technician
- Ice buildup on coils or the outdoor unit
- Unusual grinding, squealing, or banging noises
- Water pooling near the indoor unit
- Repeated breaker trips after basic checks
- Suspected refrigerant leaks or low refrigerant
HomeCallPro connects homeowners with licensed, background-checked HVAC technicians for emergency dispatch 24/7 at +1 (858) 477-5941.
Preventing Future Breakdowns
- Replace air filters regularly — every 1–3 months depending on usage and filter type.
- Schedule seasonal tune-ups before summer and winter, when demand on the system is highest.
- Keep the outdoor condenser unit clear of leaves, debris, and overgrown landscaping.
- Don't ignore minor noises or smells — small issues caught early are almost always cheaper to fix than full breakdowns.
- Clean condensate drain lines periodically to prevent clogs that lead to water damage.