Carrier Error Code On: Timer on (Mini-Split)

Updated October 16, 2026 · by Aurora Star Tech Inc.

Carrier error code On on a mini-split means: Timer on. It is also called Carrier diagnostic code On.

Low severityMini-SplitCarrier DLFSHB high wall indoor

Homeowner? What Carrier code On means for you

Usually minor Your ductless mini-split is reporting: Timer on. This code is usually informational or minor. The safe checks below often clear it; call us if it keeps showing up.

Safe things you can check yourself

Check the remote: fresh batteries and the right mode (Cool, Heat or Auto).
Check the breaker and the outdoor disconnect; both should be ON.
Open the front cover of the indoor unit and rinse the washable filters if they are dusty; let them dry before putting them back.
Keep the outdoor unit clear of snow, ice and leaves.
Try one reset: turn the power off for 30 seconds, then back on. If the code comes back, stop resetting and call a technician.

Call (647) 657-2977 Book a service call

Licensed technicians serving Vaughan, Toronto and the GTA.

What does Carrier error code On mean?

Timer ON is set.

Applies to: DLFSHBH high wall indoor units 09-24K (Midea / Carrier / Viessmann) on DLC multi-zone or single-zone outdoor units

Safety: Gas, electrical and refrigerant work must be done by a licensed technician. Turn off power and gas before servicing, never bypass a safety control, and always follow the manufacturer's manual for your exact model.

Carrier models that use code On

DLFSHBH09XAK DLFSHBH12XAJ DLFSHBH12XAK DLFSHBH18XAK DLFSHBH24XAK

Other Carrier Mini-Split codes

Code	Meaning
ODU P4	Discharge temperature protection (outdoor board)
ODU P5	Condenser high temperature (outdoor board)
ODU P6	Inverter module (IPM) fault (outdoor board)
ODU PH	Compressor pre-heat
ODU RO	Oil return cycle
Off	Timer off
P0	Inverter module (IPM) fault
P1	Over or under voltage protection
P2	Compressor top overheat (OLP)
P3	Low outdoor temperature cut-off in heating
P4	Compressor drive fault
P7	IPM temperature sensor fault

All Carrier Mini-Split error codes →

Carrier code On: homeowner questions

What does Carrier code On mean?

Timer on. Timer ON is set.

Is it safe to keep using my ductless mini-split with code On?

Usually yes. Code On is normally minor, but if it keeps coming back have it checked.

Can I reset Carrier code On myself?

You can try one reset (power off for 30 seconds, then on). If Carrier code On comes back, the cause is still there and a licensed technician should check it.

Who can fix Carrier code On near me?

Aurora Star Tech Inc. repairs Carrier ductless mini-splits in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.

Homeowner help: AC Running But Not Cooling: What to Check · Heat Pump Not Heating or Blowing Cold Air

Troubleshooting guides

Indoor unit leaking water All brands · Mini-Split
Poor capacity / high head All brands · Mini-Split
Water leaking All brands · Mini-Split
Discharge the inverter capacitors before service Carrier · Mini-Split
Display shows a strange code or does not answer the remote - DLFSHB indoor Carrier · Mini-Split
Multi-zone: one room heats, another will not cool - DLC multi-zone Carrier · Mini-Split
Read live data with the outdoor check button (SW1) Carrier · Mini-Split
Run the automatic wiring / piping correction Carrier · Mini-Split

Source: Midea DLFSHBH09XAK indoor display table (photo, 2026-10-16); Carrier MS-DLFSHB-01 High Wall Ductless Service Manual (04/2021), Display Function p.12. Written in our own words as a summary; always check the original manual.

General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.