The short answer
When a Trane AC won’t turn on in Northern Virginia, the cause is usually something you can check in ten minutes: the thermostat set wrong, a switch or breaker off, a clogged filter, or a drain safety switch that shut the system down. Work through those in order. If the outdoor unit hums but won’t start, sits silent while the thermostat calls for cool, or its fan won’t spin, it’s a part, most often a capacitor or a contactor, and that’s a call.
Check these first
From Trane’s own AC troubleshooting page, plus what we see in the field:
- The thermostat. Set to Cool, fan on Auto, set a few degrees cooler than the room. If it takes batteries, put in fresh ones. Blank screen? That’s power (blank screen guide).
- The wait. Trane thermostats hold the compressor off for 5 minutes after it stops, per the XL824 guide. Give it 5 minutes. A Wait or Starting Soon message is that delay (what Wait means).
- The indoor switch. A light switch on the wall by the furnace or air handler. The AC needs the indoor unit running.
- The breakers. The AC usually has one for the indoor unit and one for the outdoor unit, plus a disconnect box by the outdoor unit. If one tripped, don’t flip it back; call. Something made it trip.
- The filter. A clogged one can freeze the coil and shut cooling down. Trane says every 30 to 90 days.
- The drain. A float switch shuts the system off when the condensate drain backs up. Water in the drain pan is the giveaway.
- The outdoor unit. Two feet of clearance around it, no plants or leaves packed against the sides.
The $67 Heating Check
We check your furnace, heat pump or boiler before winter. Through December 31. See the offer
What the outdoor unit is telling you
Stand by the outdoor unit while the thermostat calls for cool. From our price book:
Swipe to see all columns →
Swipe to see all columns →
| What you notice | What it usually is | Typical repair |
|---|---|---|
| Hums but won’t start | The capacitor, which gives the motors their kick | $240 to $370 |
| Silent while the thermostat calls | The contactor, the switch that powers the unit | $290 to $425 |
| Runs but the fan on top doesn’t spin | The condenser fan motor or its capacitor (AC fan not spinning) | $1,100 to $1,500 |
| Ice on the lines or the coil | Low airflow from the filter, or low refrigerant | Filter, or refrigerant $190 to $740; if it needs it again, there’s a leak |
| Nothing at all, even with power | Wiring, a board or a safety that tripped | $99 diagnostic |
Trane’s own compressor page says only a trained tech should touch the wiring, for your safety and so you don’t void the warranty. A capacitor can hold a charge after the power’s off, too. Look and listen; don’t open the panel.
If the thermostat shows an alert
On an XL824, XL850, XL1050 or UX360, read it first. Err 126 means the thermostat lost the equipment (Err 126 guide); the rest are in our Trane error codes guide. A message instead of a number? See thermostat messages. A frozen screen clears with a reboot, and the other signs of a failing thermostat are in Trane thermostat not working.
If it’s a heat pump
A Trane heat pump is the same outdoor unit doing both jobs, so if it won’t cool, it may not heat either. In winter, see Trane heat pump not heating for what’s normal and what isn’t. Running but blowing warm? That’s its own guide: Trane AC not cooling. More on what we fix is on our AC repair page, and every brand’s lights and codes are in our error codes and warning lights guide.
Book it
Call (703) 997-9757 or book from our AC repair page. The diagnostic is $99, and you get the problem and the price in writing before any work starts. If your Trane is a heat pump, the same outdoor unit heats the house all winter, and our heating check is $67 per system; book that one from goswiftpro.com/cookiesoffer and a box of warm cookies comes with the visit. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Questions people ask
Why won’t my Trane AC turn on?
Usually the thermostat setting, a switch or breaker off, a clogged filter or a drain safety switch. If the outdoor unit hums but won’t start, or stays silent while the thermostat calls for cool, it’s usually the capacitor or the contactor.
Not on the outdoor unit. Reboot the thermostat, or turn off the indoor unit’s breaker for 20 to 30 seconds and back on. If a breaker tripped by itself, don’t reset it; call a tech.
Why does my Trane AC hum but not start?
Most often a failed capacitor, the part that gives the compressor and fan their kick to start. It runs $240 to $370 to replace in Northern Virginia.
How long should I wait after changing the thermostat?
Five minutes. Trane thermostats hold the compressor off for 5 minutes after it stops, so it won’t restart right away.
Can I replace a Trane AC capacitor myself?
Trane warns that DIY repairs can void the warranty, and a capacitor holds a charge even with the power off. Have a tech do it.
The system we put in first
Built to take a beating. Put in by our crew.
Heat lamps, snow and rain on one outdoor unit: that’s Trane’s own film. We’re a Trane Comfort Specialist, on Trane’s own dealer locator, and when you pick a Trane, our crew puts it in.
Films: Trane’s own.
