York Aircon LU Error Code & Blinking Light
Use this York LU guide to capture the fault correctly and see what should be checked before parts are quoted.
What does York LU mean?
York LU is listed as frequency limiting by power in Inverter Split, Multi-Split rows such as York P Series 9K-12K 115V wall-mounted ductless. The loaded row is source-backed by official diagnostic material. Confirm the exact model, series, or signal row before accepting a parts quote.
Voltage, current, fuse, module, or power-supply protection has been triggered.
Loose connector, damaged harness, or outdoor electrical component fault.
PCB or inverter-module issue after power and load checks are confirmed.
What to do now
Use these steps before customer action or a parts quote.
Treat it as a fault signal
Stop repeated restarts if LU returns, trips power, smells burnt, or the outdoor unit runs unusually hot.
No manufacturer reset steps listed for LU
Capture the complete LU pattern and model stickers first. The selected source row lists no customer reset procedure; do not treat a generic power-cycle as manufacturer guidance.
Send these to us
LU error code and blinking light, a clear display photo and blinking-light video if the unit shows one, York model stickers, affected rooms, operating state when the code appeared, and trip timing and outdoor-unit behaviour
Source-specific guidance
These diagnostic-reference notes help match the code to the exact model. Electrical, refrigerant, wiring, resistance, and component checks are technician work, not DIY steps.
| Source detail | What it says |
|---|---|
| Diagnostic note | Check power supply and outdoor power-board condition if capacity is limited. |
| Singapore / model note | YorkNow / Johnson Controls P Series technical-guide row. Use for the listed P Series 9K-12K 115V wall-mounted ductless family, not as a Singapore YHFF fault-code table. |
- Source detail
- Diagnostic note
- What it says
- Check power supply and outdoor power-board condition if capacity is limited.
- Source detail
- Singapore / model note
- What it says
- YorkNow / Johnson Controls P Series technical-guide row. Use for the listed P Series 9K-12K 115V wall-mounted ductless family, not as a Singapore YHFF fault-code table.
What to check before repair
Use this split to separate safe evidence capture from the tests a technician should prove before quoting parts.
| You can check | Technician should confirm |
|---|---|
| Before taking any system action on LU, take a clear display photo and blinking-light video if the unit shows one. | Confirm whether LU is voltage, current, module, fuse, or protection related. |
| Capture the York indoor and outdoor model stickers so the correct family row is used. | Check incoming voltage, connectors, inverter module, and current draw under load. |
| The selected source row lists no customer reset procedure. Note whether one room, several rooms, or the whole system is affected. | Confirm downstream loads before replacing electrical boards or modules. |
- You can check
- Before taking any system action on LU, take a clear display photo and blinking-light video if the unit shows one.
- Technician should confirm
- Confirm whether LU is voltage, current, module, fuse, or protection related.
- You can check
- Capture the York indoor and outdoor model stickers so the correct family row is used.
- Technician should confirm
- Check incoming voltage, connectors, inverter module, and current draw under load.
- You can check
- The selected source row lists no customer reset procedure. Note whether one room, several rooms, or the whole system is affected.
- Technician should confirm
- Confirm downstream loads before replacing electrical boards or modules.
What changes the next step
These clues decide whether the first check is room-side, shared outdoor-side, refrigerant-side, source-table, or model-family confirmation.
| What you see | What it points to |
|---|---|
| Only one indoor unit shows LU. | The affected room, indoor board path, wiring route, or local component should be checked first. |
| Several rooms or the outdoor unit show the same LU fault. | Prioritise the shared outdoor side, power path, and source-listed system branch. |
| The fault remains displayed or returns during operation. | Start with the source-row diagnostic branch before approving parts. |
| The model family is different from the row you found online. | Use the model or series filter first; same-looking codes can still belong to different diagnostic tables. |
| The model belongs to Inverter Split, Multi-Split rows such as York P Series 9K-12K 115V wall-mounted ductless. | The loaded row is source-backed by official diagnostic material. Use the matching source row before quoting parts. |
- What you see
- Only one indoor unit shows LU.
- What it points to
- The affected room, indoor board path, wiring route, or local component should be checked first.
- What you see
- Several rooms or the outdoor unit show the same LU fault.
- What it points to
- Prioritise the shared outdoor side, power path, and source-listed system branch.
- What you see
- The fault remains displayed or returns during operation.
- What it points to
- Start with the source-row diagnostic branch before approving parts.
- What you see
- The model family is different from the row you found online.
- What it points to
- Use the model or series filter first; same-looking codes can still belong to different diagnostic tables.
- What you see
- The model belongs to Inverter Split, Multi-Split rows such as York P Series 9K-12K 115V wall-mounted ductless.
- What it points to
- The loaded row is source-backed by official diagnostic material. Use the matching source row before quoting parts.
Electrical module or wiring decision
York LU needs voltage, current, module, and load checks before parts are quoted. The repair path depends on whether the fault is supply-side, wiring-side, or board-side.
Supply voltage and load checks separate building-side issues from unit-side faults.
Module or inverter faults need measured current and voltage evidence.
Repeated electrical trips should not be cleared repeatedly without diagnosis.
York LU questions
What does the York LU error mean?
Can I fix a York LU error myself?
Is it safe to keep running the aircon with an LU error?
What causes a York LU error?
Will a York LU error need a repair or a full replacement?
What should I send a technician about a York LU error?
Confirm the fault
Share the error code, model number and symptoms so we can assess the likely cause.
Not the right code?
Browse the full York list or check a few codes in the same fault category.
Ready to get started?
Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.
Read next
Use these if the quote mentions the parts, checks, or repair path this code points to.