HVAC Troubleshooting Guides
Start with the symptom. Each guide has likely causes, safe DIY steps, and when to stop and call a pro.
Why Is My Air Conditioner Not Blowing Cold Air? Causes, Fixes & Costs
Your AC is running but the air coming out of the vents is room-temperature or warm.
Furnace Not Turning On or Won't Ignite: 6 Common Causes
You hear the furnace start but the burners never light, or the whole system stays silent.
AC Freezing Up: Why Ice Forms and How to Stop It
You see ice on the refrigerant lines, indoor coil, or outdoor unit.
Condenser Fan Not Spinning: Diagnosis & Repair Costs
The outdoor unit is humming but the fan on top isn't spinning.
High Electric Bill from AC: Why It Jumped and How to Fix It
Your SCE, PG&E, or LADWP bill spiked and you're sure the AC is the cause.
Thermostat Not Working: Blank Screen, Won't Change Temp, or Not Turning On AC
Your thermostat is blank, unresponsive, or the HVAC system isn't responding to setpoint changes.
AC Not Turning On? 7 Causes, DIY Checks & Repair Costs
You set the thermostat to cool and nothing happens — no outdoor fan, no indoor blower, no click.
AC Leaking Water Inside the House? Causes and Fixes
Water is dripping from the indoor unit, staining the ceiling, or pooling around the air handler.
Furnace Blowing Cold Air: 6 Causes and How to Fix Them
The furnace runs but the air from the vents is cool or room temperature instead of warm.
AC Making Loud Noise? What Each Sound Means
The air conditioner is banging, screeching, buzzing, rattling or humming louder than usual.
HVAC Short Cycling: Why Your System Turns On and Off Repeatedly
The system starts, runs for only a few minutes, shuts off, and restarts again minutes later.
AC Smells Bad? What Musty, Burning and Rotten Egg Odors Mean
A noticeable odor comes from the vents when the air conditioner or heater runs.
AC Stopped Working Suddenly? Emergency Checklist and Costs
The air conditioner was cooling fine and then stopped completely, often during the hottest part of the day.