EN

Severity: Minor

Goodman AC / Heat Pump Error 1dL – Causes & Fix

IdL (often read as 1dL) is not a fault: the furnace is powered and waiting for a call from the thermostat.

Safety first · Consult a professional

If you smell gas, leave the house now, don't use light switches or phones inside, and call 911 or your gas utility from outside. If a CO alarm sounds, get everyone out, call 911 and don't restart the furnace until it has been inspected. Only check the thermostat, filter, service switch and blower door yourself – never open the burner compartment or touch the gas valve.

  • Gas appliance: no DIY repairs. If you smell gas, leave the building, do not use switches and call your gas utility’s emergency line from outside.
  • Carbon monoxide is odorless. Keep a CO alarm near fuel-burning appliances; if it sounds, get everyone outside and call 911.
  • Unplug the appliance or switch off the breaker before opening any panel. Mains voltage can kill.

At a glance

Severity: 1/5 – Minor1/5

Severity: Minor

Meaning
IdL – Furnace Idle, Waiting for Thermostat
Typical repair cost
$5–$800
DIY difficulty
Very easy

Goodman, Amana and Daikin-brand furnaces with a three-digit seven-segment display show "IdL" when the control is in stand-by. The first character is a capital I, not a one – it stands for idle, meaning the furnace has power and simply isn't being asked to heat or run the blower. So it is not an error and not an ignition lockout. If the house is cold while IdL is showing, the furnace is fine but the request from the thermostat never arrives: a setting, dead batteries, a loose wire or a communicating thermostat that lost its link. The display also rotates through status items, so if IdL alternates with another code, that other code is the real message.

How it looks on the display

Goodman Air Conditioner / Heat Pump display showing error 1dL

Model families & display variants

Model familyShowsNote
GMVM97 / GCVM97 modulating furnacesIdLAfter power-up the display shows the unit address, then enters the status menu where IdL is the resting state.
Newer GR9S / GC9S-family furnaces with 7-segment displayId LSame stand-by message; the status menu cycles each item for about 2 seconds with a 1-second gap.
Amana and Daikin-brand furnaces and some air handlersIdLBuilt on the same control family, so IdL means idle here too.
Search spelling1dLPeople read the capital I as a one; there is no separate 1dL fault code.

Symptoms

  • "IdL" or "Id L" on the furnace control's three-digit display, visible through the blower door window
  • No heat although the thermostat seems to be set to heat
  • Burners and inducer never start – the furnace stays silent
  • In summer: no blower on a cooling call while the display keeps showing IdL
  • IdL alternating every few seconds with a different code
  • IdL appeared right after a new thermostat was installed

Possible causes

Ranked by how often each cause is behind this code (editorial estimate).

  1. Thermostat not calling: mode set to off or cool, setpoint below room temperature, schedule or hold in the way 30%
  2. Dead batteries or a blank thermostat screen 20%
  3. Loose or wrong thermostat wire (R, C, W, Y, G) at the thermostat or the furnace terminal board 20%
  4. Communicating thermostat not paired or lost communication with the furnace 10%
  5. Heat-pump or dual-fuel settings keeping the furnace from being called 10%
  6. Another fault code shown alongside IdL that actually explains the problem 5%
  7. Control board not reading the thermostat input 5%

Fix it step by step

Diagnostic flow: 1dL1Confirm it really is IdL2Set the thermostat to call3Check thermostat power4Check the easy furnace items5Look at the thermostat wires6Watch while the thermostat calls

  1. Confirm it really is IdL

    Look through the sight window on the blower door and watch the display for at least 15 seconds. If only IdL appears, the furnace sees no request; if another code shows between the IdL cycles, look up that code instead.

    Tools: Flashlight

  2. Set the thermostat to call

    Switch the mode to Heat and raise the setpoint at least 3–5 °F above room temperature. Cancel any schedule, vacation hold or eco mode, and check the thermostat isn't waiting out a compressor or cycle delay.

  3. Check thermostat power

    Replace the batteries if the thermostat uses them. A thermostat that's completely blank on a C-wire can mean a blown 3-amp low-voltage fuse on the furnace board – that's a job for a technician, especially if it blows again.

  4. Check the easy furnace items

    Make sure the furnace service switch is on, the blower door is fully seated so the door switch is closed, and the filter isn't packed with dust. These won't cause IdL by themselves but they rule out a second problem once the heat call arrives.

  5. Look at the thermostat wires

    With the thermostat pulled off its base, check that each wire is firmly clamped under the right terminal and that no bare copper touches a neighbor. If you just replaced the thermostat, compare the labels with the old one – a missing W or C connection is the classic result.

    Tools: Screwdriver

  6. Watch while the thermostat calls

    With the thermostat calling for heat, the display should change from IdL to a heating status within a minute. If it stays on IdL, the signal isn't reaching the furnace and a technician needs to trace the wiring or the pairing.

How to reset 1dL

  1. Turn the thermostat mode to Off, wait a minute, then back to Heat with a higher setpoint
  2. If nothing changes, switch the furnace service switch off for 30 seconds and back on once
  3. Watch the display: after the address and startup items it should go to IdL, then change to a heat status when the thermostat calls

Where the parts are

Split AC / heat pump: indoor and outdoor unit – 1dL123456
Split AC / heat pump: indoor and outdoor unit
  1. 1Fan
  2. 2Temperature sensor
  3. 3CAN bus
  4. 4Outdoor unit
  5. 5Compressor
  6. 6Engine computer (ECM)

Repair options & costs

RepairDIY?Estimated cost
Thermostat batteries and settings Yes $5–$15
Thermostat wire repair by a technician No $120–$300
Thermostat replacement, installed No $150–$450
Furnace control board replacement (rarely needed for IdL) No $350–$800

Rough US estimates; technician call-out fees vary by region. Not a quote.

When to call a technician

Call a licensed HVAC technician if the thermostat is clearly calling for heat and the display stays on IdL, if the thermostat is blank on a C-wire, or if a newly installed thermostat won't pair. Also call if IdL alternates with a fault code you can't clear with one reset. Anything beyond the thermostat, filter, service switch and blower door belongs to the technician on a gas furnace.

Frequently asked questions

Is 1dL an error code on my Goodman furnace?

No. It reads IdL, with a capital I, and means idle. The furnace is powered and ready, but it hasn't received a heat, cool or fan request.

Why does it show IdL and I have no heat?

Because the call for heat isn't reaching the furnace. Start with thermostat mode, setpoint and batteries, then the thermostat wires; a furnace that never gets the request can't start.

IdL keeps switching to another code – which one matters?

The other one. The status menu rotates through the operating mode and any active faults, so IdL is just the mode and the second code tells you what's wrong.

I installed a new thermostat and now it only shows IdL. What did I miss?

Usually a wire: W not connected, R and C mixed up, or a missing C so the thermostat can't power its relays. Communicating models also have to be set up as communicating with the furnace, otherwise no call is sent.

Sources