A Trane furnace that will not light or a Trane air conditioner that runs without cooling in Menlo Park, Atherton or Portola Valley rarely has a failed compressor. Far more often it is an igniter, a flame sensor, a pressure switch, a capacitor, a contactor or a slow refrigerant leak. The job is to prove which one before a part is ordered, and on Trane’s communicating systems that starts at the thermostat.
What Trane makes for homes
Trane’s home line is built around ducted equipment: gas furnaces, central air conditioners, heat pumps, air handlers and indoor coils, plus thermostats and air cleaners. Many Trane outdoor units use Trane’s own Climatuff compressor. The range runs from single-stage systems to TruComfort variable-speed systems, which change compressor and blower speed to hold the temperature closely. The top systems communicate through Trane’s ComfortLink II controls.
Trane furnaces: what fails, in the order it fails
Most no-heat calls on a Trane gas furnace follow the furnace’s own startup sequence, and so does the diagnosis:
- Inducer and pressure switch. The inducer fan clears the vent before the burners light. If the switch does not close, the furnace stops there. A blocked vent, a cracked hose or a full condensate trap is as likely as a bad switch.
- Igniter. Hot surface igniters crack with age, and a hairline crack is not always visible.
- Flame sensor. A coated sensor lets the burners run for a few seconds and then shuts them down. Cleaning often fixes it, and a reading of the flame signal confirms whether it did.
- Limit switch. A furnace that heats, stops and restarts usually has an airflow problem: a clogged filter, closed registers or a weak blower.
The control board’s blinking light, visible through the door window, narrows the search; note the pattern before you switch the power off. More on furnace repair.
Air conditioners and heat pumps
Trane outdoor units fail mostly on the electrical side: a weak capacitor, a pitted contactor or a tired fan motor. Heat pumps add a reversing valve and defrost controls, so a heat pump that blows cool air in winter, or ices up and does not clear, needs those checked. Cooling that fades over several weeks means a leak, and we find it before adding refrigerant. See AC repair and heat pump repair.
ComfortLink II systems
On a ComfortLink II system, the thermostat, the indoor unit and the outdoor unit share information over communicating wiring. The system recognizes its own components and reports faults on the thermostat screen. In practice:
- stored faults are read before any meter comes out, and they often say which unit raised the alarm;
- a replacement board or thermostat has to be set up so the system accepts it;
- pairing the system with a non-communicating thermostat or part can leave it running, but without its variable-speed features.
Warranty registration and records
Register the furnace or air handler, the coil and the outdoor unit. Each has its own serial number, and a claim on any of them starts with that number and the installation date. Keep the installation invoice, the registration confirmation and a record of yearly service. Bought the house with the system in place? Check whether it was registered and what the warranty document says about later owners. Parts coverage does not include labor, as our warranty page explains. We are independent and not affiliated with Trane.
Repair or replace
Electrical parts, sensors, igniters and drains are repairs. A cracked heat exchanger is different: it can let combustion gases into the air in the house, and replacing the furnace is the usual answer. On the cooling side, an older Trane that still runs on R-22, a refrigerant no longer produced, is usually a replacement conversation once it has a major leak or a compressor failure. Replacement estimates are free, and larger repairs come with written next steps.
Local notes
Many Menlo Park ranch homes have a Trane furnace in the garage, a hall closet or the attic, with central air added years later on the original ducts, so the ducts and the filter slot are part of the diagnosis. On wildfire-smoke days, people often run the fan with a denser filter. If that filter is too restrictive for the system, the furnace can trip its limit switch and the AC coil can freeze, so ask us which filter your system can take before smoke season.