My furnace turns on and off rapidly. What is wrong?

That pattern is short-cycling. The most common causes are a dirty filter, a failing flame sensor, a thermostat in a bad location, or a furnace oversized for the house. Most are inexpensive to fix once we diagnose. Annual maintenance catches this before it strands you.

How much does furnace repair cost?

The service call is a flat $49, credited toward your repair once you approve the work. Common repairs (igniter, flame sensor, capacitor, control board) get a written price after diagnosis, and you approve it before any work starts. Larger jobs (blower motor, heat exchanger) are quoted the same way, in writing, and the invoice matches what you approved. Every repair is backed by a one-year labor warranty.

Should I repair or replace an older furnace?

Past 15 years old and facing a repair that runs half the cost of a new install, replacement usually wins on efficiency and reliability. We lay out both numbers and let you decide. We do not commission-sell replacements. The replacement path is covered at HVAC installation.

Do you service heat pumps in heating mode too?

Yes. Heat pump repair is some of our most common work, especially in newer Bay Area construction: reversing valves, defrost controls, refrigerant charge, contactors. Ducted and ductless mini-split systems both.

Is a cracked heat exchanger really dangerous?

Yes. A cracked heat exchanger can leak combustion gases (including carbon monoxide) into the indoor air. If we find one, the furnace gets red-tagged and we walk you through the options the same visit. If you suspect CO right now, call us or step outside and call 911.

Furnace Repair in the Bay Area | Onzone Heating and Cooling

Furnace Repair.

It is 6am, the house is 54 degrees, and the furnace clicks but does not fire. Onzone runs same-day furnace repair across the Bay Area. Gas, electric, heat pump, dual-fuel, residential and commercial.

Every gas system we touch gets a combustion safety check and a written diagnostic report. No-heat calls jump to the front of the queue every time.

Problems we fix every day.

No heat from vents

The thermostat calls, the furnace or heat pump runs, and the rooms never warm up. Somewhere between the call and the vents, a part is not doing its job.

Furnace short cycles

Start, stop, restart, over and over. Short cycling usually traces to airflow restrictions, flame sensing, a tripping limit, or thermostat trouble, and we test each one instead of guessing.

Ignition or pilot failure

A gas furnace that clicks and sparks but never lights has a short suspect list: igniter, gas valve, burners, or a safety control doing its job. We work the list until it lights and stays lit.

Heat pump stuck cooling

A heat pump blowing cool air in heating mode points to the reversing valve, defrost controls, a sensor, or the refrigerant charge. We check them in order and fix the one that actually failed.

Sage Vikky May 2026

I had an amazing experience with Oleg and Teymur! They repaired my AC and furnace, and also installed a new water heater for me. From the beginning they were friendly, professional, and really knew what they were doing. They took the time to explain everything, answered all my questions, and made me feel comfortable throughout the process. It's hard to find people who truly care about doing quality work, but these guys definitely do. Everything is working perfectly now, and I'm very happy with the results. I highly recommend Oleg and Teymur to anyone looking for honest and reliable service!

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Sally Siao June 2026

I can't say enough good things about the OnZone team. They fixed our basement radiant floor heating which had not been working for over two years. Another company made three separate service visits and still couldn't solve the problem, but OnZone diagnosed and fixed it successfully. Their entire process was outstanding—from scheduling the appointment, to completing the work, to following up afterward. The team was professional, knowledgeable, and easy to work with. I highly recommend OnZone to anyone looking for HVAC or plumbing services. They exceeded my expectations, and I will definitely refer them to my friends.

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Artur D June 2026

Oleg did a great job at our house: he fixed malfunctioning AC unit, adjusted and tuned up a Heater, which is located in the attic. He was punctual and on-time as agreed, and spent time to make sure everything was tested and functioning properly before he left. His prices are very reasonable too. Will call him again if need comes as he is well versed in plumbing and electrical. I am very happy with his services.

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Furnace Repair.