The short answer
When a Trane thermostat in Northern Virginia shows Wait, Starting Soon or a flashing Cool On, it’s holding the system off on purpose. The compressor just shut off, or the power just came back after an outage, and the thermostat waits a few minutes so the compressor doesn’t restart too soon. Give it 5 minutes. If it never starts, or it starts, stops and waits over and over all day, that’s a real problem, and the message is only covering for it.
Why it waits
Trane’s own page on a flashing Cool On gives two reasons:
- The compressor just stopped. Restarting it right away can overheat it or make it short cycle, so the thermostat holds it off for a while first.
- The power just came back. An outage can bring a surge that’s hard on the compressor, so the thermostat delays startup after the power returns.
How long? Trane’s XL824 installer guide sets a minimum off time of 5 minutes for the compressor and 1 minute for indoor heat. So an AC or heat pump that just shut off waits about 5 minutes, and a furnace about a minute. Trane notes that thermostats show it differently: Cool On flashing, Starting Soon, or Wait.
The $67 Heating Check
We check your furnace, heat pump or boiler before winter. Through December 31. See the offer
What you’re seeing, and what to do
From the troubleshooting tables in Trane’s XL824 and UX360 guides:
Swipe to see all columns →
Swipe to see all columns →
| What you see | What it means | What to do |
|---|---|---|
| Wait, Starting Soon or Cool On flashing | A startup delay protecting the compressor | Give it 5 minutes |
| The same thing right after an outage | A startup delay after the power came back | Give it 5 minutes |
| Heating or Cooling shows, but the vents blow nothing warm or cool | The blower waits a moment as the equipment starts | Wait a minute and check the vents again. If nothing changes, the equipment needs a look |
| A + under the indoor temperature | The heat pump and the indoor backup heat are both running | Nothing. Trane says it’s there for information |
| The fan runs all the time | The fan is set to On, Circulate or Clean | Set it to Auto. If it still runs, it’s wiring or a fault in the indoor unit, like a tripped heating limit |
When Wait is hiding a problem
- It never starts. If the delay ends and the outdoor unit still sits there, work through Trane AC not turning on. Humming but not starting is usually the capacitor, $240 to $370; silent while the thermostat calls is usually the contactor, $290 to $425.
- It starts, stops and waits all day. That’s short cycling, and the delay is the thermostat protecting a compressor that keeps getting shut off. Check the filter first, then see short cycling.
- The screen is blank or frozen. That’s power or a stuck screen, not a delay: blank screen and how to reset it.
- An alert number shows. Read it first. Err 126 is lost communication (Err 126 guide); the rest are in our Trane error codes guide. A word instead of a number? See thermostat messages.
One thing not to do: don’t flip the breaker off and on to skip the delay. When the power comes back, the thermostat starts a fresh one. And if a breaker tripped by itself, flipping it back on can make the cause worse, so have a tech find it.
If it keeps happening in winter
On a heat pump, a long pause with steam off the outdoor unit is usually defrost, not a delay. Our Trane heat pump not heating guide covers what’s normal, and Trane emergency heat covers when to switch to backup heat.
What a visit costs
A diagnostic visit is $99, and you get the problem and the price in writing before any work starts. Our heating check is $67 per system, through December 31: furnace, heat pump or boiler. If you want every brand’s codes and lights in one place, our error codes and warning lights guide has them.
Book it
Book the heating check, call (703) 997-9757, or book online 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 does my Trane thermostat say Wait?
It’s delaying the compressor on purpose, after the compressor just shut off or after a power outage, so it doesn’t overheat or short cycle. Give it 5 minutes.
How long does a Trane thermostat wait before starting?
Trane’s XL824 installer guide sets a 5 minute minimum off time for the compressor and 1 minute for indoor heat.
What does Starting Soon mean on a Trane thermostat?
The same thing as Wait or a flashing Cool On: a startup delay that protects the compressor. It clears on its own.
Why is my Trane thermostat flashing Cool On?
It’s holding the AC or heat pump off for a few minutes after it stopped or after the power came back. If the outdoor unit never starts once the delay ends, have it checked.
What does the + on my Trane thermostat mean?
The heat pump and the indoor backup heat are running at the same time. Trane says it’s there for information, and nothing needs to be done.
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.
