Ruud equipment in San Leandro homes is mostly gas furnaces in hall closets, garages and attics, often paired with a Ruud air conditioner or heat pump outside. When a Ruud furnace will not heat, short-cycles or blows cold air, a useful visit follows the heating sequence in order (safety, thermostat, ignition, flame sensing, pressure switch, venting, blower and airflow) and finds where it stops before anything is replaced. Ruud shares its heritage and manufacturing with Rheem, so most of this applies to Rheem furnaces too. We are an independent service company, not affiliated with Ruud.
Safety first
A gas smell, a burning smell, flame rollout (flames or scorch marks outside the burner area), repeated breaker trips or rough, banging ignition are urgent. Turn the furnace off at its switch. If you smell gas, leave the house and call the gas company or 911 from outside before you call us. For anything else that cannot wait, see emergency HVAC service.
How a Ruud furnace starts
- The thermostat calls for heat.
- The inducer motor starts to push air through the vent.
- The pressure switch proves the vent is drawing.
- The igniter heats up.
- The gas valve opens and the burners light.
- The flame sensor proves the flame within a few seconds; if it cannot, the gas valve closes.
- After a short delay the blower starts and warm air reaches the registers.
- Limit switches watch the temperature the whole time, and the blower runs on briefly after the burners stop.
Where the sequence stops tells us where to look:
| Where it stops | What you notice | Usually points to |
|---|---|---|
| Nothing happens | No sound from the furnace | Thermostat, power, door switch, fuse or control board |
| Inducer runs, no ignition | A hum but no glow or flame | Pressure switch, vent or condensate blockage, cracked tubing |
| Igniter glows, no flame | Glow, then a retry | Gas supply, gas valve or a weak igniter |
| Lights, then shuts off in seconds | Short burst of flame | Flame sensor, ground or flame quality |
| Runs a few minutes, then shuts down | Short cycling | Limit trip from a dirty filter, restricted return, weak blower or blocked coil |
| Blower runs, air is cold | Cold air from the vents | Ignition lockout, gas supply, or a limit keeping heat off |
Pressure switch codes are not a parts order
A pressure-switch fault can come from a vent restriction, a condensate problem, a weak inducer, cracked or blocked tubing, or a real safety issue. On a high-efficiency condensing furnace, a clogged condensate trap or drain is one of the most common causes. Replacing the switch without finding why it opened usually brings the same code back.
Airflow and limit trips
Dirty filters, restricted returns, weak blowers, a blocked AC coil above the furnace and crushed ducts can all overheat the furnace and trip the limit switch, which looks like a control board failure. Many post-war homes here have a single small return and ductwork in the attic or crawlspace, so we check static pressure and the duct runs before blaming the furnace. Damaged runs are covered under duct repair.
What you can check yourself
- The filter is clean and installed in the right direction.
- The thermostat is set to heat, a few degrees above room temperature, with fresh batteries if it uses them.
- The furnace door is fully closed; a door safety switch keeps the furnace off when it is loose.
- The furnace switch and breaker are on.
- Count the flashes of the status light; the code chart is usually printed inside the door.
Ruud lines, cooling equipment and parts
Ruud equipment comes in lines such as Ruud Select, Achiever, Achiever Plus and the Ultra Series, with staged and variable-speed models in the higher lines and EcoNet or Comfort Control2 controls on some systems. Ruud air conditioners and heat pumps, most built around scroll compressors, are covered on our AC repair and heat pump repair pages. On the furnace side, an igniter, flame sensor or pressure switch is usually a same-visit repair because technicians carry common parts; a control board or variable-speed blower motor is matched to the model and serial number and may need ordering. Covered parts keep their manufacturer’s warranty, with registration usually deciding how long, and the repair itself carries our 90-day warranty.
Repair or replace
Repair usually makes sense when diagnosis finds one clear ignition, sensor, pressure, blower or airflow fault. Replacement becomes more realistic with a heat exchanger concern, repeated major failures, severe airflow problems or an old furnace. Our furnace repair vs. replacement guide walks through it.
Local notes
In San Leandro, San Lorenzo and Castro Valley heating runs mostly from November to March, so a Ruud furnace sits unused for months before its first cold-night start, and that is when a dirty flame sensor or a cracked igniter shows up. A furnace tune-up in the fall finds them first.