Change your HVAC air filter
The single most common cause of 'my AC isn't cooling' calls is a blocked filter.
What you'll learn
- What MERV rating is right for most San Diego homes (MERV 8–11)
- How to find your system's filter size (16×25×1 or 20×25×1 is typical)
- Why filter direction matters, arrows point toward the air handler
- When to swap (every 90 days, sooner with pets or wildfire smoke)
Step by step
- Turn the thermostat off (not the breaker).
- Find the return-air grille, wall, ceiling, or a slot at the furnace.
- Slide the old filter out. Note the arrow direction on the frame.
- Insert the new filter arrow pointing toward the furnace.
- Turn the thermostat back on.
Safety note
If the filter is black, fuzzy, or wet, the system has been running under strain. Book a tune-up before something more expensive fails.
Rather have a pro handle it?
We match homeowners with licensed local HVAC pros across San Diego County. Our operators answer the phone, not a call center.
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