AC not cooling: what to check, common causes and repair cost
For Silicon Valley homes · Updated October 2026 · Sources below
Start with the easy checks: the thermostat is set to Cool, the breaker is on, the filter is clean and the outdoor unit is running and clear. If it still blows warm, the usual causes are dirty coils, a refrigerant leak or a failing part like a capacitor, fan or control - all jobs for a technician. Low refrigerant means there's a leak, so adding more without fixing it doesn't last.
The short version
- Check first: thermostat on Cool, breaker on, clean filter, outdoor unit running
- Dirty filters and coils can cause malfunctions and early compressor or fan failure (DOE)
- Low refrigerant means a leak - a trained technician should fix it, test it and recharge
- Water dripping indoors usually means a clogged condensate drain
- Typical AC repair: about $172 - $664 (national)
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What it costs
- AC repair$172 - $664 (average $417)
- Recharge refrigerant (after the leak is fixed)$200 - $500
Typical ranges from published cost guides - mostly national figures. Bay Area prices usually run higher. Your actual price depends on your home and the job, and a pro gives you the real number. Source: HomeAdvisor cost guide (national) (Jun 2026). Have a quote? Check it with the Quote Explainer
Signs you need a technician
- The air from the vents is warm or barely cool after the easy checks
- The outdoor unit hums but the fan doesn't spin, or it doesn't start at all
- Ice on the refrigerant lines or the indoor coil
- The system turns on and off every few minutes
- Water leaking around the indoor unit or furnace
- The breaker trips when the AC starts
Repair or replace?
- Usually worth repairing: a capacitor, contactor, fan motor, thermostat, clogged drain line or a small, findable refrigerant leak.
- Consider replacing: a failed compressor or a major leak on an older system, or a system that uses R-22 refrigerant (common before 2010), which is getting hard to find.
- If the furnace is near the end too, get a quote for a heat pump - it replaces both the AC and the furnace.
In Silicon Valley
- Replacing an AC or heat pump needs a permit in California. Under the state energy code, properly permitted work triggers any required HERS testing, and HERS paperwork is needed to close the permit. You can ask your contractor for the completed HERS forms.
- If you're replacing, local electricity providers such as San José Clean Energy and Silicon Valley Clean Energy offer rebates for heat pumps that replace gas heating. SVCE says to apply before the system is installed.
- Bay Area Air District rule: starting in 2029, only zero-NOx furnaces can be sold or installed in the Bay Area. It applies to new equipment only, and the Air District has said it may adjust the timeline.
Questions homeowners ask
Why is my AC running but not cooling?
The common causes are a dirty filter or coils, low refrigerant from a leak, a failing control or fan, or a thermostat that's misreading the room. Check the thermostat setting and the filter first. If the air is still warm or you see ice on the lines, turn the system off and call a technician.
What should I check before calling for AC repair?
Make sure the thermostat is set to Cool and below room temperature, and that its batteries are good. Check the breaker, replace a dirty filter, and make sure the outdoor unit is running and not blocked by plants or debris. Keep the thermostat out of direct sun so it reads the room correctly.
Does my AC just need more refrigerant (Freon)?
If it's low, it's leaking - refrigerant isn't used up. The Department of Energy says a trained technician should fix the leak, test the repair and charge the system correctly. Adding refrigerant without fixing the leak wastes money.
How much does AC repair cost?
National cost guides put AC repair at about $172 to $664, with an average around $417, and a refrigerant recharge at about $200 to $500. Bay Area prices usually run higher, and a compressor or a major leak costs much more.
Why is water leaking from my AC inside the house?
Usually the condensate drain line is clogged, so water from the indoor coil backs up and overflows. Turn the system off, catch the water and call a technician to clear the line. A frozen coil melting can also cause it.
Should I repair or replace my old AC?
Repair a small, inexpensive failure. Get a replacement quote too if the compressor has failed, there's a large leak, or the system uses R-22 refrigerant. If the furnace is also old, a heat pump can replace both, and local rebates can help with the cost.
Is a broken AC an emergency?
It can be during a hot spell if an older adult, a baby or someone with a health condition is at home - go somewhere cool while you wait for a repair. If you smell burning or the breaker keeps tripping, turn the system off and leave it off until it's checked.
Do you need a permit?
Yes - replacing heating or AC equipment needs a permit in California.
General guidance based on California's building code - your city can have stricter rules, and zoning, historic and HOA rules can apply too. Check with your city's building department before you start.
Check the rule for your cityRebates: Heat pump heating & AC
- San José Clean Energy EcoHome Rebates
- Silicon Valley Clean Energy Home Rebates
- Silicon Valley Power Residential Rebates
- City of Palo Alto Utilities Rebate Hub
- Central Coast Community Energy rebates
Rebate programs change often and money runs out. Amounts are from each program's page as of Oct 2026 - always confirm on the program page, and check whether you must apply before you buy or install.
See the rebates for your ZIPQuestions to ask the pro
- What exactly failed, and can you show me?
- If it's a refrigerant leak, where is it and how will you fix it before recharging?
- Is this repair worth it on a system this age?
- What would a replacement or a heat pump cost, with rebates?
- How long are the parts and labor warrantied?
Before you sign, check the contractor's license at cslb.ca.gov. How to hire a contractor in California
Need a heating & AC pro?
Tell us about the job in 2 minutes - free. We send it to one local pro at a time, never a crowd.
Related answers
Sources
- U.S. Department of Energy - Common air conditioner problems
- HomeAdvisor - AC recharge cost guide (refrigerant and leaks)
- California Energy Commission - HERS program (testing on HVAC changes)
- Silicon Valley Clean Energy - Home rebates
- Switch Is On - San José Clean Energy heat pump rebate listing
- Bay Area Air District - Rules 9-4 and 9-6 fact sheet (furnaces and water heaters)
General information for Silicon Valley homeowners, not professional advice for your home. Rules and programs change - check the source, and have a licensed pro look at your situation.