The short answer
Most thermostat messages in Northern Virginia homes aren’t errors. A flashing “Heat On” or “Cool On” is the thermostat waiting out a built-in delay of up to about five minutes that protects the compressor. “Recovery” means it’s warming the house ahead of your schedule. “Aux Heat” means a heat pump is getting help from its backup heat. The ones worth a call are a wait that never ends, a blank screen, and a heat pump stuck on Aux all day in mild weather.
What each message means
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| Message | What it means | What to do |
|---|---|---|
| “Heat On” or “Cool On” flashing (Honeywell) | The compressor protection delay. The thermostat holds the call for up to about five minutes after the system last ran | Wait it out. Still flashing after ten minutes means something past the thermostat isn’t answering |
| “Waiting For Equipment” (Honeywell touchscreens) | The same delay, in words | Give it five minutes. Longer than that, the furnace or heat pump is the problem. Here’s what it looks like |
| “Wait” or “Starting Soon” (Trane) | The same delay on a Trane or American Standard thermostat | Give it five minutes. More on the Trane Wait message |
| “Recovery” | Warming or cooling early so the house hits the next schedule setting on time | Nothing. It’s doing its job |
| “Temporary Hold” | You changed the temperature by hand. It holds until the next schedule period | Nothing, unless you want the schedule back now |
| “Permanent Hold” | It holds your setting until you cancel it. The schedule is off | Cancel the hold to get the schedule running again |
| “Aux Heat” | The heat pump is getting help from the backup heat strips | Normal in a cold snap or right after you bump the setting up. On all day in mild weather, call |
| “Em Heat” | Emergency heat: the outdoor unit is off and the strips heat the house alone | Use it only while the heat pump is down. It costs more to run |
| “Calibrating” (ecobee) | Measuring the room for a few minutes after a restart | Wait |
| Filter reminder | A timer, not a sensor. It doesn’t know how dirty the filter is | Check the filter, change it if it’s gray, reset the reminder |
| “Fan On” | The blower runs nonstop, even between heating cycles | Switch it to Auto if the air feels cool between cycles. Why the air feels cold in winter |
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.
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The $67 Heating Check
We check your furnace, heat pump or boiler before winter. Through December 31. See the offer
When the wait never ends
A flashing Heat On or Waiting For Equipment that lasts more than ten minutes means the thermostat is calling and nothing is answering. The thermostat is usually fine. Check these, in this order:
- The furnace switch, a light switch on or near the furnace, is on.
- The breaker for the furnace or air handler isn’t tripped.
- The furnace door is on tight. It presses a safety switch, and a loose door cuts the power.
- The condensate drain isn’t backed up. Many systems have a float switch that kills the call when the pan fills.
If all four check out, here’s what it means when the thermostat says heat but the house is cold, and our post on a furnace that won’t turn on goes step by step.
A blank screen
Start with the batteries if it takes them. A wired thermostat with no batteries runs on power from the furnace through the C wire, so a blank screen often means the furnace lost power, not the thermostat. The same four checks apply: furnace switch, breaker, door, condensate float switch.
If those are fine, the usual cause is a blown 3 or 5 amp fuse on the furnace control board, often right after a thermostat wire touched something it shouldn’t. A blown fuse usually means a short somewhere, so replacing it without finding the short just blows the next one. That part’s ours. More in thermostat not working, and on a Trane, the signs it’s failing.
Codes in words: communicating thermostats
A Carrier Infinity, Trane ComfortLink or Lennox iComfort talks to the furnace and heat pump directly and shows their fault codes on the screen. The code is the same one blinking on the furnace board, so our furnace blinking light guide reads it. Nest has its own letters and numbers: here are the Nest error codes and what it means when Nest says the system is delayed. On a Daikin One Touch, here’s what a communication error means.
Aux and Em Heat, and what they cost
Backup heat strips are electric resistance heat, and they cost more to run than the heat pump. A short stretch of Aux on a cold morning is the system working as designed. Hours of Aux at 45 degrees outside is a heat pump that isn’t pulling its weight. The full breakdown is in aux heat vs emergency heat, and the best thermostat setting for winter keeps Aux from kicking on when it doesn’t need to. On a Trane heat pump, here’s when to use EM HEAT. On a Goodman that runs and runs on Aux, here’s why the heat pump isn’t heating.
Our heating check is $67 per system, through December 31: furnace, heat pump or boiler. We check the thermostat wiring and the calls it sends while we’re there.
Book it
A repair visit starts with a flat $99 diagnostic, or $250 after hours, and you get the price of the fix before we touch anything. Call (703) 997-9757, day or night, or book online from goswiftpro.com/cookiesoffer by November 30 and a box of warm MOLTN cookies comes with the heating check. Every current deal is on our offers page. 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 is Cool On or Heat On flashing on my thermostat?
It’s the compressor protection delay. The thermostat waits up to about five minutes after the system last ran before it starts it again. If it’s still flashing after ten minutes, the equipment isn’t answering.
What does Waiting for Equipment mean?
The thermostat is holding the call during its built-in delay. If the message lasts more than ten minutes, check the furnace switch, the breaker, the furnace door and the condensate drain.
Why is my thermostat screen blank?
Dead batteries, or the furnace lost power and the thermostat lost it with it. Check the furnace switch, breaker, door and condensate float switch. A blown fuse on the furnace board is the next cause.
What does Aux Heat mean on my thermostat?
Your heat pump is getting help from the backup heat strips. That’s normal in a cold snap. If Aux runs all day in mild weather, the heat pump needs a look.
