TL;DR: For furnace repair in Corona, CA, call a licensed contractor who handles both plumbing and HVAC, since most furnaces here run on the same gas line a plumber inspects. Before you call, check the thermostat batteries, the furnace power switch, the breaker, and the air filter. If you smell gas near the unit, leave the house first and call 911 or the gas utility’s emergency line before calling anyone for repair. RT Olson Plumbing, Heating and Air Conditioning diagnoses and repairs furnaces across Corona and the surrounding Inland Empire, holds CSLB license #997337, and answers calls 24/7.
If your furnace near Dos Lagos or Eagle Glen kicked on this morning and blew cold air instead of heat, or didn’t kick on at all, you probably don’t know yet whether this is a five-minute fix or a service call. Here’s how to sort that out before you dial, and why the company you actually want isn’t always a standalone “HVAC guy.” In a lot of Corona homes, it’s a licensed plumbing and HVAC contractor who already works on the gas line feeding the unit.
Is furnace repair a plumbing job or an HVAC job?
Furnace repair is HVAC work, but because most furnaces in Corona run on natural gas, the license that covers the gas connection and the license that covers the furnace’s mechanical side are often held by the same contractor. California splits these into separate trade classifications (C-20 for HVAC, C-36 for plumbing and gas piping); you can verify any contractor’s license through the state board before they step inside.
That matters because a dead furnace isn’t always a furnace problem. Sometimes it’s a closed gas shutoff valve, a corroded gas line fitting, or a venting issue that touches both trades. A contractor licensed for plumbing and HVAC can run down the whole chain, thermostat to gas valve to burner, in one visit instead of sending you to a second company.
What should you check before you call anyone?
Before you schedule anything, run through four quick checks, because a lot of “no heat” calls turn out to be something you can fix in under a minute.
- Thermostat: confirm it’s set to Heat (not Cool or Off), the batteries are fresh, and the set temperature is above the current room temperature.
- Furnace switch: most furnaces have a light-switch-style power switch on or near the unit. Check it’s flipped to ON, not accidentally bumped off during storage or cleaning nearby.
- Breaker and filter: check the electrical panel for a tripped breaker, and pull the air filter. A filter clogged with dust (common in homes along the 91 corridor) can choke airflow enough to trip a safety limit switch and shut the whole system down.
- Gas smell: if you smell a rotten-egg odor near the furnace or gas meter, stop checking anything else. Leave the house immediately, don’t flip switches or light anything, and call 911 or the gas utility’s 24-hour emergency line from outside. Only after the utility confirms the scene is safe should you call a plumber or HVAC technician for the repair itself.
If those four checks don’t bring the furnace back, it’s time to call for a diagnostic visit.
Why is my furnace blowing cold air instead of heat?
Cold air from the vents almost always means the blower fan is running but the burners never ignited. The usual suspects are a dirty or failing flame sensor, a worn-out hot surface igniter, or a gas valve that isn’t opening on command.
The flame sensor is a small metal rod near the burner that confirms a flame is actually present; if it’s coated in carbon buildup, the control board reads it as “no flame” and shuts the gas valve for safety, even though the blower keeps pushing air. A technician checks this with a microamp reading on the sensor rather than guessing from symptoms alone. It’s also worth checking the thermostat isn’t set to “Fan: On,” which runs the blower continuously whether or not the burners are firing. Our heating repair breakdown for the region covers more of these failure patterns and what each one typically takes to fix.
When does it make more sense to replace the furnace instead of repairing it?
Replacement usually wins once repair costs approach half the price of a new furnace, or the unit is past 15 to 20 years old and starting to fail in multiple places at once. A single bad igniter on a 6-year-old furnace is an easy repair; a cracked heat exchanger on a 19-year-old unit is a replacement conversation.
Newer furnaces also run meaningfully more efficient. ENERGY STAR certified furnaces hit higher AFUE ratings than units built two decades ago, which shows up on the gas bill over a winter, not just in the repair estimate. We laid out the full decision process, including the 50% rule, in Furnace Repair or Replace? if you want to run the numbers before a technician is even on site.
Who should you actually call for furnace repair in Corona?
Call a licensed, local contractor who can diagnose both the furnace and the gas line feeding it in the same visit, rather than a furnace-only shop that has to refer out gas work. RT Olson Plumbing, Heating and Air Conditioning has served Corona since 2014, holds CSLB license #997337, and takes calls 24/7, which matters for a furnace that quits on a cold night rather than during business hours.
From offices in Corona and Anaheim, the team covers furnace repair and full HVAC installation across Corona, Riverside, Eastvale, Norco, and the rest of the surrounding service area. A technician checks the control board, the flame sensor, the gas valve, and the venting before recommending anything, and gives you a written diagnosis before any repair work starts.
If the four checks above didn’t solve it and there’s no gas smell involved, call RT Olson at (951) 344-5596 to get a technician scheduled.
About RT Olson Plumbing, Heating and Air Conditioning
RT Olson Plumbing, Heating and Air Conditioning is a licensed plumbing and HVAC contractor (CSLB #997337) serving Corona, CA and the surrounding Inland Empire since 2014, with additional operations out of Anaheim. The company holds a 4.9 Google rating across 619 reviews and answers calls 24/7 for plumbing and heating and cooling repairs.