Daikin AC / Heat Pump Error L5 – Causes & Fix
L5: the outdoor inverter saw a current spike on the compressor output and shut the compressor down.
At a glance
Severity: High
- Meaning
- Inverter Output Overcurrent (Compressor)
- Typical repair cost
- $0–$3,800
- DIY difficulty
- Hard
Daikin defines L5 as output overcurrent detection: the inverter in the outdoor unit measured a sudden current surge on the wires feeding the compressor and cut the output within milliseconds to protect its power transistors. The system retries several times and locks out if the spikes keep coming. When L5 appears the instant the compressor tries to start, the compressor is often mechanically stuck or the power module on the inverter board is shorted. When it only appears after running for a while on a hot afternoon, the compressor is being overloaded – a matted outdoor coil, a slow outdoor fan or too much refrigerant. Loose compressor terminals and weak supply voltage complete the list.
How it looks on the display
Model families & display variants
| Model family | Shows | Note |
|---|---|---|
| Wall-mounted ductless heads (FTX, FTXS, Emura) | L5 | The indoor lamp blinks; the code is read out with the remote's check function. |
| SkyAir and ducted systems with wired controller | L5 | Shown directly, sometimes with the outdoor unit address. |
| Outdoor unit service LEDs | LED pattern | The outdoor board's LEDs give a matching pattern that technicians read against the service manual. |
Safety first · Consult a professional
The outdoor inverter board stores several hundred volts DC in its capacitors for minutes after power-off, and the compressor terminals connect straight to it. Limit yourself to the breaker, the disconnect and cleaning the outside of the coil with the power off. Refrigerant checks need an EPA 608-certified technician.
- Unplug the appliance or switch off the breaker before opening any panel. Mains voltage can kill.
Symptoms
- L5 on the wired controller or read out through the remote's check mode
- Outdoor fan runs but the compressor never gets going, or stops after a few seconds
- Unit cools for a while, then stops in the hottest part of the day
- Clicking or a short buzz from the outdoor unit at every start attempt
- Code comes back after resets and finally the unit stays locked out
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Compressor mechanically locked, worn bearings or shorted winding
- Power module (IPM) or inverter board defective
- High head pressure from a dirty outdoor coil, blocked airflow or slow outdoor fan
- Loose or burnt compressor terminal connections
- Refrigerant overcharge, liquid returning to the compressor or stop valve left closed after install
- Low or unstable supply voltage
Fix it step by step
Note when it trips
Watch one start attempt. L5 within seconds of the compressor starting points to a stuck compressor or failed power module. L5 after 10–30 minutes of cooling on a hot day points to overload. Telling the technician which one saves diagnosis time.
Clean and clear the outdoor unit
With the disconnect off, remove leaves, grass clippings and cottonwood fluff from the coil fins and keep at least 1 ft of open space around the unit. Rinse the coil gently from the inside out with a garden hose – no pressure washer.
Tools: Soft brush, Gloves
Check the outdoor fan
Restart the system and confirm the outdoor fan spins up smoothly. A fan that stalls or turns slowly makes the head pressure – and the compressor current – climb until L5 trips.
Give the unit a long power-off
Switch off the breaker for 10 minutes. The lockout clears and the inverter capacitors discharge. Restart once; if L5 returns immediately, stop trying so a damaged compressor isn't hammered by more restarts.
Let the technician test compressor vs. board
A technician measures the three compressor windings (they should be low and equal, and fully isolated from ground) and checks the power module. Daikin service techs can also use an inverter checker in place of the compressor to prove whether the board itself is at fault.
Tools: Multimeter
How to reset L5
- Turn the system off with the remote or controller
- Switch off the outdoor breaker for 10 minutes
- Restore power and start once; if L5 comes back at once, leave it off and call a technician
Where the parts are
- 1Fan
- 2Temperature sensor
- 3CAN bus
- 4Outdoor unit
- 5Compressor
- 6Engine computer (ECM)
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Clean outdoor coil and clear airflow | Yes | $0–$150 |
| Technician diagnosis of compressor and inverter | No | $120–$250 |
| Repair compressor terminal wiring | No | $150–$350 |
| Outdoor inverter board replacement | No | $600–$1,400 |
| Compressor replacement incl. refrigerant recovery | No | $1,800–$3,800 |
Rough US estimates; technician call-out fees vary by region. Not a quote.
When to call a technician
Call a technician if L5 returns after cleaning the outdoor coil and one long power reset, and immediately if it trips the moment the compressor starts. Repeated restarts on a locked compressor can burn the windings and turn a board repair into a compressor replacement.
Frequently asked questions
Does L5 always mean the compressor is dead?
No. The inverter board, a loose terminal or simple overload from a dirty coil trigger the same protection. Only winding and insulation measurements, or a test with an inverter checker, tell the two apart.
Why does L5 only happen on the hottest afternoons?
High outdoor temperatures raise head pressure, and a coil clogged with dirt or cottonwood makes it worse. The compressor then draws more current until the inverter trips. Cleaning the coil often solves this pattern.
Is replacing the compressor on an older system worth it?
On a system near the end of its life, a compressor plus the required refrigerant work can approach the price of a new outdoor unit. Get the diagnosis in writing and compare both options.
Is L5 the same as U0 on my Daikin?
No. U0 flags a refrigerant shortage, while L5 is about current on the compressor output. A system low on charge can cause other codes, but L5 itself points at the compressor, the inverter or an overload.
Sources
- Official Daikin user documentation and support pages (facts only; wording is our own)
- Methodology: How We Build Code Pages · Data Sources We Use · Editorial Policy