How quickly can you come out?

Call by noon and standard service calls go out the same business day. No-heat and no-cool emergencies run on the 24/7 line, with a senior tech typically on-site within a few hours.

Do you charge a diagnostic fee?

The service call is a flat $49 and covers the trip and the time it takes to find the problem. Approve the repair and that $49 rolls into the repair cost, so you never pay twice. Every repair is backed by a one-year labor warranty.

Will you service my brand of system?

Almost certainly. We service every major North American HVAC brand plus the common mini-split manufacturers. If we genuinely cannot handle it, we say so up front and the trip costs you nothing.

HVAC service & Repair in the Bay Area

HVAC Service.

The AC quits on the hottest week of the year, or the furnace clicks and will not fire on a cold morning, and suddenly every hour matters. Onzone runs same-day service across the Bay Area for any make, any age, residential or commercial.

Our techs arrive with the parts to actually fix it, not just write a diagnosis and leave. Flat diagnostic fee. Repair price up front, in writing. Most calls end with the fix done on the first visit.

Problems we fix every day.

AC won't start

Outdoor unit silent, blower never starts. We trace power, thermostat, capacitor, and control problems until we find the failed link in the chain.

Uneven room temperatures

Hot rooms here, cold rooms there. The usual suspects are airflow restrictions, failed dampers, refrigerant problems, or a thermostat sensor misreading the room.

Furnace blows cold air

When the heat cycle fails, we test it end to end: ignition, flame sensing, gas valve operation, limits, pressure switches, and board signals. The step that fails names the part.

System short cycles

Constant starting and stopping wears equipment out fast. Dirty coils, weak capacitors, safety trips, refrigerant charge, and control faults all cause it, so we test rather than swap parts on a hunch.

Cathy Nelson June 2026

OMG they were a lifesaver! After a power outage my old A/C would not come on in the middle of this heat wave we're having. I went through thumbtack and received several notifications back of companies that wanted to help. Ozone was the first one. I was thrilled that they could fit me in at a 2 PM to 4 PM timeslot as I was having people over for dinner tonight and expected 92° weather. He got here he was very quick clean explained everything and reasonable. I was a little hesitant because I didn't see many reviews but it's because they're a newer company and they just haven't got them yet and I figured I'd take a chance. Boy am I glad I did. They're coming tomorrow to give me an estimate on two new heaters and two new air conditioners.. I was very happy with their service and you will be too if you find yourself in need you can't go wrong with these guys! 5 star for sure!!

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Oksana Sytnyk June 2026

I called ONzone Heating & Cooling because my AC was not cooling properly. They responded very quickly and scheduled a same-day service appointment. Teymur arrived on time and was very professional, friendly, and easy to talk to. He carefully inspected the system, explained what was causing the issue, and walked me through the repair process step by step. I really appreciated that he took the time to answer all my questions and made sure I understood what was being done. It's not often that you meet a technician who is both highly knowledgeable and genuinely cares about the customer. The problem was fixed quickly, and my AC has been working perfectly since. Teymur is someone you can trust, and I would definitely recommend ONzone Heating & Cooling to anyone looking for honest and reliable HVAC service.

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Roma Govorko June 2026

Oleg did an excellent job with our HVAC system. He was professional, knowledgeable, and very easy to work with. He arrived on time, carefully diagnosed the issue, and explained the repair options in a clear and honest way. The work was completed efficiently and with great attention to detail. Everything was left clean, and the system is now running perfectly. It's clear that Oleg takes pride in his work and genuinely cares about providing quality service. I highly recommend Oleg to anyone looking for a reliable and experienced HVAC specialist. I would not hesitate to hire him again for future heating and air conditioning needs.

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HVAC Service.