The short answer
On a Daikin One+ thermostat in Northern Virginia, an alert pops up on the screen, white for minor and yellow for critical, and the list of past ones is under system optimization, then error history. The most common are communication errors, where the thermostat lost touch with the furnace, air handler or heat pump. Those are usually a loose or swapped wire or a power problem at the equipment, not the thermostat. Restart it first. If the alert comes back, write the code down and call. A visit starts with a $99 diagnostic.
Where to find the alerts
- On the screen: a new alert pops up with the dealer’s contact info. You can dismiss it or restart the thermostat from there.
- Error history: menu, then system optimization, then error history. Each entry shows the code and when it happened.
- White or yellow: white alerts aren’t critical. Yellow ones are, and the system may not heat or cool until it’s fixed.
From the Daikin One+ homeowner guide and the Daikin One error code list.
The $67 Heating Check
We check your furnace, heat pump or boiler before winter. Through December 31. See the offer
What the thermostat codes mean
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| Code | What it means | What it usually is |
|---|---|---|
| 05 | Communication problem on the equipment bus | Loose, crossed or broken data wire |
| 0B, 0C, 0D | Thermostat sensor hardware | The thermostat itself |
| 0E, 0F | Wi-Fi problem | Your router, the password, or distance |
| 10 | The thermostat rebooted | A power blip; fine if it’s once |
| 1E | Lost contact with the heat pump | Wiring or power at the outdoor unit |
| 1F | Lost contact with the AC | Wiring or power at the outdoor unit |
| 20 | Expansion valve coil problem | A part in the indoor coil |
| 21 | Lost contact with the air handler | Wiring or power at the air handler |
Communication errors
A Daikin One+ talks to communicating equipment over two data wires, and Daikin’s list of causes is short: the two data wires reversed, the equipment lost power, or a wire that’s loose, cut or broken. That’s why it shows up after a power outage, a remodel, or someone pulling the thermostat off the wall. A heat pump showing 11 or E11 usually means its startup test was never run, which is an install item, not a broken part.
Wiring details are in the Daikin One+ install guide.
Furnace codes on a Daikin system
The thermostat doesn’t always repeat the furnace’s own code. Daikin’s DM97MC and DC97MC furnaces show theirs on a display inside the door, and the meanings match Goodman’s boards, since Daikin owns Goodman.
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| Furnace display | What it means |
|---|---|
| On | Normal |
| E0 | Lockout after failed tries to light |
| E1, E2 | Pressure switch problem |
| E3 | High limit open |
| E4 | Flame where there shouldn’t be one |
| E5 | Blown fuse |
| E6 | Weak flame signal |
| E7 | Igniter |
| EA | Polarity |
| Ed | Rollout switch |
| EC | Inducer overcurrent |
To see the last few, hold the fault recall button 2 to 5 seconds until the display goes blank, and each stored code shows for 2 seconds. From the DM97MC furnace manual. The Goodman versions of these codes are in our Goodman furnace codes chart.
What you can do yourself
- Restart it. Menu, settings, system setting, thermostat, then restart thermostat.
- Wi-Fi codes. Menu, settings, Wi-Fi, and rejoin your network. A pairing code for the app expires after 15 minutes, so get a fresh one if it fails.
- A blank screen. The thermostat runs on 24 volts from the C and R wires at the equipment. Check the furnace or air handler switch, its breaker and the furnace door, then call. The clock keeps time about 3 hours without power.
- Reading off by a few degrees. Calibration is under system optimization. Put the thermostat in off mode and give it about 30 minutes.
Don’t swap the data wires or open the equipment. If a carbon monoxide alarm is going off or you smell gas, that comes first.
What it costs
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| Cause | How you’d know | What fixing it costs |
|---|---|---|
| Power or a tripped switch at the equipment | Blank screen, every comm error at once | Nothing if it’s a breaker |
| Loose or crossed data wire | 05, 1E, 1F or 21 after a power outage or a remodel | Priced in writing before any work starts |
| A failed equipment board | The same comm error with good wiring | $550 to $1,180 for a new board |
| The thermostat itself | 0B, 0C or 0D | $300 to $640 to replace it |
The tech reads the error history and the equipment’s own codes, checks the data wires end to end and the 24 volt supply, and gives you the price in writing before any work starts. Other thermostat problems are in our thermostat guide. Our heating check is $67 per system through December 31, for a furnace, heat pump or boiler.
We fix Daikin furnaces, heat pumps and air handlers across Northern Virginia, in Ashburn, Leesburg, Sterling, Herndon, Chantilly, Fairfax, Arlington and Manassas.
More Daikin: Daikin mini split error codes; a blinking green light on a Daikin mini split; the Daikin One Touch thermostat; Daikin mini split troubleshooting. Daikin owns Goodman and Amana, so their furnace codes are in our Goodman furnace codes chart, and other brands are in our error codes and warning lights guide.
Get it fixed
Call (703) 997-9757 and we’ll get a tech out to look at your Daikin system. We answer day or night. Rather book online? Pick a time here and a box of warm cookies comes with the visit. A repair visit starts with our $99 diagnostic, and you get the price in writing before any work starts. Already have a quote? We’ll give you a free second opinion. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Questions people ask
Where do I see error codes on a Daikin One+ thermostat?
New alerts pop up on the screen. Past ones are under menu, system optimization, error history.
What does a communication error on a Daikin One mean?
The thermostat lost contact with the furnace, air handler or outdoor unit. It’s usually the two data wires reversed, a loose or broken wire, or power lost at the equipment.
How do I restart a Daikin One+ thermostat?
Menu, settings, system setting, thermostat, restart thermostat. If an alert comes back after a restart, write the code down and call.
Why is my Daikin One+ screen blank?
It gets power from the furnace or air handler through the C and R wires. Check that equipment’s switch, breaker and door. If they’re fine, a tech needs to trace the 24 volt supply.
