The short answer
Whether the whole house is cold, a few rooms never warm up, or the heater runs with odd noises or smells, the cause is usually traceable in one visit. We repair furnaces, heat pumps, wall heaters, floor furnaces and ductless units in Sunnyvale and explain the findings before any work.
Sunnyvale winters rarely get harsh, but a run of gray, damp days makes a house without working heat feel cold quickly, especially in the mornings. Our team is based in Los Altos, a short 4-mile drive from neighborhoods in 94085, 94086, 94087 and 94089, and we repair every common type of home heating found in the city. Rather than listing equipment, this page is organized around the situation you are actually facing, because the first question we ask is not what you own but what the house is doing.
Situation One: The Whole House Is Cold
When nothing is producing heat, the cause is often at the beginning of the chain. A thermostat with dead batteries or a lost schedule, a tripped breaker, a furnace switch accidentally turned off, or a clogged filter that triggered a safety shutdown can each stop heat entirely. If those check out, the fault is usually in the ignition system of a gas furnace, the control board, or, on a heat pump, a failed outdoor fan, compressor component or reversing valve.
We start at the thermostat and confirm the call for heat reaches the equipment, then work through the heater's sequence until we find where it stops.
Situation Two: Some Rooms Never Warm Up
If the heater runs and most of the house is comfortable, the problem is usually distribution. In Sunnyvale's many single-story homes, ducts run through the attic or under the floor, and a disconnected or crushed run can send a room's warm air into the crawlspace. Rooms at the end of long duct runs, rooms over a garage, and additions tied into the original system are the usual trouble spots.
We measure temperatures and airflow at the registers in the cold rooms, inspect the duct runs serving them, and check whether a return path exists. Closed doors without a return can starve a bedroom of airflow.
- Disconnected or torn ducts in the attic or crawlspace
- Dampers left closed after a previous service
- Registers blocked by furniture or rugs
- An addition connected to a system that was never sized for it
Situation Three: Heat Comes With Noise or Odor
A heater that works but sounds or smells different deserves a look before it fails completely. Squealing often means a blower motor or belt is wearing out. A boom when the burners light points to delayed ignition. A burning-dust smell that fades within the first hour of the season is normal; one that persists, or any electrical burning smell, is not. A rotten-egg odor may mean a gas leak: leave the house and call your gas utility from outside.
Heat pumps make their own sounds, including a whoosh during defrost and occasional clicks as valves shift. If those sounds become loud grinding or rattling, call for service.
Situation Four: An Older Wall Heater or Floor Furnace
Some Sunnyvale homes still rely on gravity wall heaters or floor furnaces, either as the main heat or for one part of the house. These simple heaters fail at the pilot, thermocouple or gas valve, and their grilles collect dust that can scorch. We repair them when parts are available and the unit passes a safety check. If the combustion chamber is damaged or parts are no longer made, we explain that clearly and discuss options, such as a ductless heat pump head for the area it serves.
A Short Pre-Season Checklist
A few minutes before the first cool week can prevent many of the calls we get in late fall.
- Replace the furnace or air handler filter
- Test the thermostat and replace batteries if it uses them
- Clear stored items away from the furnace and wall heater
- Make sure carbon monoxide alarms work on every floor
- Run the heat briefly on a mild day to catch problems early
When Repair Is No Longer the Right Call
For heaters near the end of their life, it helps to know that Bay Area Air District rules require gas furnaces manufactured from 2029 to meet a zero-NOx standard, which in practice points replacements toward heat pumps. The rules do not require replacing working equipment. We will tell you plainly whether a repair makes sense or whether planning a replacement is the better use of your money.
More services in Sunnyvale
- AC Repair in Sunnyvale
- Heat Pump Installation in Sunnyvale
- AC Installation in Sunnyvale
- Furnace Repair in Sunnyvale
