Power and Wiring Lookups
F1 Error Code on Air Conditioners
An F1 error code air conditioner owners see is often tied to power or wiring rather than refrigerant. On Mitsubishi Electric outdoor units, F1 points to reverse phase detection or incorrect power and connection wiring between the units. For most other major brands, F1 is either not used or not something we could verify. Here is what the documentation shows, brand by brand.
At a Glance
What Is the Short Answer for F1?
Only one brand on our list publishes an F1 meaning we could confirm. Mitsubishi Electric outdoor units in the standard inverter range use F1 when they detect negative phase, meaning the phase order of the supply is reversed, or when the power or connection wiring between indoor and outdoor units is incorrect.
That makes F1 most relevant to three phase installations and to systems that have recently been installed, moved or rewired. It is far less likely to appear out of nowhere on a system that has run happily for years, although supply changes can still trigger it.
For every other brand, we say plainly that the meaning is unconfirmed or that the brand uses a different code layout. Guessing would do more harm than good, because power faults should never be treated casually.
Brand Table
How Does Each Brand Treat F1?
Read the entry for the brand printed on your unit. Where we have no confirmed meaning, we explain the brand’s own format and link to its library so you can find the right code.
Mitsubishi Electric: confirmed
F1 on the standard inverter outdoor range indicates that negative phase has been detected, or that power or the connection between the indoor and outdoor units is incorrect. Related codes include F2 for an open phase. Start with the Mitsubishi code library.
Mitsubishi Heavy Industries: not confirmed
MHI uses E plus a number for most faults. We could not confirm an F1 meaning on MHI equipment, so check whether your Mitsubishi badge says Electric or Heavy Industries.
Daikin: not listed
Daikin’s own error code reference includes F3 and F6, but we did not find F1. Use the Daikin code library and the remote check function to confirm what your unit is reporting.
Panasonic: different format
Panasonic F codes are protection codes with two digits after the letter, such as F91, F95 and F97. A standalone F1 is not a Panasonic code we could confirm. If you saw F1 on the remote, rerun the check routine described in the Panasonic code library.
Samsung: not confirmed
Samsung inverter codes generally use E or C with three digits. We could not confirm an F1 fault. See the Samsung code library.
Fujitsu: different format
Fujitsu codes are two characters counted from blinking lamps or shown on a wired controller. F1 is not part of the scheme we could confirm. The Fujitsu code library explains the lamp patterns.
LG: different format on splits
LG split and ducted systems use CH plus a number. LG notes that some portable and window units use other letter codes, which our pages do not cover. Visit the LG code library.
Actron: not confirmed
Actron ducted controllers report E codes, and the WC-02 controller has its own set. There is no confirmed Actron F1. See the Actron code library.
Phase Order Explained
What Does Reverse Phase Actually Mean?
Three phase power delivers electricity on three separate conductors, each peaking at a slightly different moment. The order in which they peak is called the phase sequence. Certain motors and compressors depend on that order to turn the right way.
If two phases are swapped, the sequence reverses. Some equipment would then run backwards, which can damage a compressor quickly. So many three phase outdoor units check the sequence at start up and refuse to run if it is wrong. On Mitsubishi Electric units, that refusal shows up as F1.
When reverse phase happens
It usually follows electrical work. A new installation, a switchboard upgrade, a meter change or a repair to the supply can all leave phases connected in a different order.
Why it matters
Phase order is not something an owner can see or test safely. It needs a licensed electrician or air conditioning technician with the right instrument.
Single phase homes do not have a phase sequence to reverse, since only one active conductor supplies the unit. That is one reason F1 is less common in typical suburban houses with a wall split. Even so, the wiring part of the meaning still applies to them.
The second half of the Mitsubishi Electric meaning covers wiring between the indoor and outdoor units. A swapped or poorly connected conductor at the terminal block can produce the same code, even on a single phase system.
Identify Your Unit
How Do You Confirm Which Brand Raised F1?
Correct identification avoids a lot of confusion, especially with two companies sharing the Mitsubishi name. Work through these steps before calling.
Check the front badge
Read the full brand name on the indoor unit or wall controller.Read the compliance labels
Indoor and outdoor units each carry a label with the model number and supply type. Three phase supply is normally shown clearly.Note recent electrical work
Write down any switchboard upgrade, solar installation, meter change or new circuit in recent weeks.Record the display exactly
Some controllers show a unit address beside the code. Capture everything in one photo.Check the outdoor unit for indicator lights
From a safe distance only, note whether any lights are visible. Do not remove covers to look for them.
Safety First
What Should You Never Do With an F1 Code?
Because F1 concerns the supply and the wiring, the list of things to avoid is longer than usual. Power faults can injure people, not just damage equipment.
Avoid these
- Opening the outdoor unit or isolator to look at the wiring
- Swapping conductors yourself to correct phase order
- Resetting breakers again and again
- Running the system with a known supply problem
Do these instead
- Switch the system off at the controller
- Note any flickering lights or other affected appliances
- Leave the breaker off if it tripped again
- Book a licensed technician and mention recent electrical work
If you smell burning, see scorch marks or hear buzzing from the switchboard or isolator, switch off at the main switch if it is safe to do so and call for help straight away.
Gentle Checks
Which Owner Checks Are Still Safe?
There are still a few useful things you can do without touching anything electrical. These help the technician understand the situation and occasionally reveal a simple cause.
- Check whether any breakers have tripped at the switchboard, without opening the switchboard cover beyond its normal door.
- Ask whether an electrician, solar installer or the electricity distributor worked at the property recently.
- Notice whether other three phase equipment, such as a pool pump or workshop machine, is behaving oddly.
- Power cycle once at the air conditioner breaker and note whether F1 appears immediately.
- Write down the time and date so the technician can match it with any supply events.
Keep a simple log if the code comes and goes. Note the time, the weather and anything else switched on in the home. Patterns linked to heavy loads, such as an oven or pool heater running at the same moment, can point toward a supply weakness.
An F1 that appears immediately at power up strongly suggests a supply or wiring condition. Mention that observation when booking, since it changes how the technician plans the visit.
On Site
How Does a Technician Diagnose F1?
The technician approaches F1 methodically, working from the supply inward. Licensed electrical work is involved, and the technicians we send hold the licences their work requires.
Supply measurement
Voltage on each phase is measured, along with phase sequence. That shows whether the supply arriving at the outdoor unit is correct.
Terminal inspection
Connections at the isolator and the outdoor terminal block are checked for tightness, correct order and heat damage.
Interconnecting wiring
The cable between the indoor and outdoor units is checked for correct termination at both ends and for damage along its route.
Board checks
If the supply and wiring are correct, the technician looks at the outdoor board’s detection circuit. Boards are only replaced after other causes are ruled out.
Where the fault lies outside the property, such as in the street supply, the technician will explain the readings so you can contact your electricity distributor.
Related Codes
Which Codes Are Close Relatives of F1?
Power and wiring problems produce a family of codes on most brands. Looking at the family helps when your display shows something slightly different.
- Mitsubishi Electric F2 indicates an open phase on the standard inverter range.
- Daikin P1 on Sky Air, VRV and packaged systems indicates power voltage imbalance or open phase.
- Daikin U1 indicates reverse phase or open phase on the ranges that use it.
- Daikin U2 indicates a power supply voltage defect or an instantaneous power failure.
- Actron documents older systems where one code covered pressure or phase problems together.
These related codes tell the same story. The unit has detected that the power arriving is not what it needs, so it refuses to run. Our U2 comparison and P1 comparison pages cover two of them in more depth.
New Installs and Relocations
Why Does F1 Often Appear Right After Installation Work?
A system that shows F1 on its very first start is telling you something about how it was connected. Installers work carefully, but terminal blocks have several conductors in a small space, and a single swap is enough to trigger the code. The same applies when a unit is moved to a new wall or a new house.
In that situation, the fix is often a correction to the wiring rather than a new part. Even so, it must be done by someone licensed, because the terminals carry mains voltage. If the original installer is still available, contacting them first is usually sensible, since the work may be covered by their workmanship guarantee.
Brand new system
Note the date of installation and the installer’s details. Share them when booking, so the technician knows the history.
Relocated unit
Moving an outdoor unit means disconnecting and reconnecting power and signal wiring. F1 straight afterwards points strongly at those connections.
Replaced outdoor unit
A new outdoor unit connected to existing indoor wiring can reveal old cabling problems. The technician checks the full run, not just the new end.
Open more detail
Some owners worry that F1 on a new system means a faulty product. That is possible, but wiring and supply conditions are far more common explanations. A technician will measure the supply and check terminations before suggesting any component is at fault.
Keep the installation paperwork somewhere easy to find. It usually lists the model numbers, the installer and the date, all of which help if warranty questions arise later.
Businesses and Larger Homes
What If F1 Appears on a Commercial System?
Three phase supply is common in shops, offices, clinics and larger homes. As a result, phase related codes appear more often on those sites. The code means the same thing, but the impact can be bigger, especially if one supply feeds several systems.
- Check whether more than one air conditioner shows a fault at the same time, which points to the shared supply.
- Note whether refrigeration, lifts or other three phase equipment has tripped or behaved strangely.
- Ask the building manager about recent work on the main switchboard or metering.
- Keep the system off until the supply has been checked, rather than restarting during trading hours.
- Have the site contact details and access arrangements ready, including after hours entry if needed.
Commercial sites sometimes have their own electrical contractor. The air conditioning technician can work alongside them, sharing readings so the supply fault is fixed at its source.
Australian Context
When Do F1 Type Faults Tend to Appear in Australia?
Electrical work is the usual trigger. Many Australian homes have added rooftop solar, batteries or switchboard upgrades in recent years. Each of those jobs touches the supply, and any of them can disturb phase order or air conditioner wiring if care is not taken.
Storms are another factor. Severe weather in Brisbane, Sydney and occasionally Melbourne and Adelaide can damage supply infrastructure, leaving one phase missing or unstable. Meanwhile, newer housing estates on the fringes of Perth and Melbourne sometimes see supply work during ongoing construction nearby.
Coastal corrosion plays a slow part too. Salt air affects isolators and terminal blocks over time, which can create poor connections on one conductor.
Booking
How Do You Book an F1 Repair?
Rapid Air Cooling takes your booking and dispatches an independent licensed technician in your area. We do not claim manufacturer accreditation and are not an agent for any brand.
Select your city for local details: Sydney air con repairs, Melbourne air con repairs, Brisbane air con repairs, Perth air con repairs and Adelaide air con repairs. For the bigger picture, see our air conditioning service Australia home page.
Please tell us about any recent electrical, solar or switchboard work when you call. That single detail often explains an F1 code.
Questions
Frequently Asked Questions
What does F1 mean on a Mitsubishi Electric?
On the standard inverter outdoor range, F1 means negative phase was detected, or the power or connection wiring between indoor and outdoor units is incorrect.
Is F1 used by Daikin?
We did not find F1 in Daikin’s own error code reference. Daikin lists F3 and F6, and uses U1 and P1 for phase problems on various ranges.
My Panasonic shows F1. Is that a code?
Panasonic F codes have two digits after the letter, such as F91 or F97. Rerun the remote check routine and read all three characters.
Can I fix reverse phase myself?
No. Changing supply wiring is licensed electrical work. Leave the system off and book a qualified technician.
Why did F1 appear after solar was installed?
Any work on the supply can change phase order or disturb wiring. Mention the installation when booking so the technician checks the supply first.
Does F1 affect single phase homes?
Phase order applies to three phase supply. However, the Mitsubishi Electric meaning also covers incorrect indoor to outdoor wiring, which can occur on any system.
Is F1 dangerous?
The code itself protects the equipment. The underlying supply or wiring problem can be hazardous, so leave covers closed and book a technician.
Keep Exploring
What Other Pages Might Help?
F1 on Your Outdoor Unit?
Leave the covers on and give us a call. We will book a licensed technician to check the supply and wiring.
Reviewed by AC repair and service specialist on 22 October 2026. How we write our articles