Panasonic Refrigerant Fault
Panasonic F91 Error Code
The Panasonic F91 error code tells you the system has spotted something wrong with how refrigerant is moving through it. In many homes that means the gas charge is low, usually from a leak, or the flow is being restricted. It is a code for a licensed technician, and this page explains why.
Meaning
What Does the Panasonic F91 Error Code Mean?
Panasonic lists F91 as a refrigerant cycle abnormality. Service documentation for residential inverters describes the detection logic in general terms. The compressor is running faster than a set point, yet the electrical current it draws stays unusually low. When that happens repeatedly within a short period, the board logs F91 and shuts down.
Why would low current matter? A compressor pumping a healthy charge of refrigerant has to work against real resistance, so it draws a predictable current. If there is too little refrigerant to pump, or the flow is blocked, the compressor spins with less effort. The board reads that light load as a sign something is wrong with the cycle.
Because the detection condition and thresholds vary between series, a technician confirms the details against the manual for your model. The broader context sits on our Panasonic error code hub.
The Refrigerant Loop
How Does Refrigerant Normally Flow in a Panasonic System?
A quick look at the cycle makes F91 easier to understand. Refrigerant travels in a sealed loop between the two units, changing between liquid and gas as it moves heat around.
Compressor
Raises the pressure and temperature of refrigerant gas and sends it on its way. It is the heart of the loop.
Condenser coil
Releases heat. In cooling, this is the outdoor coil. In heating, the indoor coil takes this role.
Expansion valve
Drops the pressure of the liquid refrigerant so it can boil and absorb heat in the next coil.
Evaporator coil
Absorbs heat. In cooling, this is the indoor coil, which is why the air coming out feels cold.
In a sealed, healthy system, the amount of refrigerant never changes. It is not consumed or used up. So a low charge always points to a leak, past or present, or to an installation that was never charged correctly.
Reading It
How Do You Find F91 With the Remote?
You will usually notice the timer lamp blinking and the system refusing to cool or heat properly. To read the code, press and hold the hidden CHECK button on the remote with a paper clip.
Aim at the indoor unit and keep holding for about five seconds until the display shows two dashes. Step through the codes with the timer arrow. When F91 is displayed and the indoor unit gives a long beep, that is the stored fault.
Write it down. F codes are protection codes, so the unit has stopped to avoid damage. Do not keep resetting it in the hope it clears.
Symptoms
What Symptoms Often Come Before F91?
A refrigerant problem rarely appears overnight. Many owners notice a slow decline before the code finally shows.
Performance signs
- Cooling or heating has weakened over weeks or months
- The unit runs for longer to reach the set temperature
- Air from the outlet feels only mildly cool or warm
- Higher power bills for the same comfort
Physical signs
- Frost on the indoor coil or on outdoor pipework
- A hissing or bubbling sound near pipe joints
- Oily residue around flare nuts or valve caps
- Freeze protection records stored in memory
Causes Ranked
What Causes a Panasonic F91 Fault?
The list runs from causes that are quick to put right through to more involved repairs. Every item requires a licensed technician to confirm and fix.
Service valve not fully open
After installation or repair, the valves at the outdoor unit must be opened completely. A partly closed valve restricts flow and is a quick fix once found.Low charge from a leak
The usual cause on established systems. Leaks often occur at flare joints, valve cores or where pipes rub against something.Incorrect charge at installation
Long pipe runs need extra refrigerant. If that was not added, the system may run short from day one.Blockage or restriction
Kinked pipes, moisture freezing at the expansion valve or debris in the circuit can starve the system.Expansion valve fault
An electronic expansion valve stuck nearly closed has a similar effect to a low charge.Current sensing issue
Less often, a fault in how the board measures current could produce a false reading. This is checked after refrigerant causes are ruled out.
Owner Checks
What Can You Safely Check for F91?
F91 is not a code owners can fix. Refrigerant work is legally restricted to licensed technicians in Australia. Still, a few checks can gather useful clues without any risk.
- Note the code and how cooling or heating has changed over recent weeks.
- Clean the indoor filters, since airflow problems can make refrigerant symptoms worse.
- Look at the outdoor unit from a safe distance for obvious damage to pipes or insulation.
- Check whether any pipe insulation is torn, chewed or missing near the outdoor unit.
- Think back to recent work, such as installation, relocation or another repair.
- Do not touch valve caps, flare nuts or pipes. Never try to add refrigerant yourself.
- Leave the system off and book a licensed technician.
Refrigerant can cause frostbite on contact and, in some modern systems, is mildly flammable. Handling it without training and a licence is unsafe and illegal.
Technician Process
How Does a Licensed Technician Fix F91?
The correct repair finds and fixes the root cause. Simply topping up the gas is not a proper repair if a leak is present.
Confirm valve positions
The technician first checks that the outdoor service valves are fully open. On new or recently serviced systems, this alone can solve F91.
Measure pressures and temperatures
Gauges and thermometers show how the system is performing. Readings compared with expected values reveal whether the charge is low or flow is restricted.
Locate the leak
Electronic detectors, bubble solution or pressure testing with nitrogen are used to find the leak point. Common spots include flare joints and valve cores.
Repair the leak
Flare joints may be remade, valve cores replaced or damaged pipe sections repaired. Larger leaks may involve coil repair or replacement.
Vacuum and recharge
The system is evacuated to remove air and moisture, then charged with the correct amount of refrigerant for the model and pipe length.
Verify operation
The technician runs the system and checks pressures, temperatures and current draw are back in the normal range.
All of this work needs an ARCtick licensed technician. The technicians we send hold the licences their work requires. Our split system regas page describes the process in more detail.
Keep Running?
Is It Safe to Keep Running a Panasonic With F91?
No. F91 is a protection code, and the system has stopped for good reason. A compressor running short of refrigerant is poorly cooled, because the refrigerant also carries heat away from the compressor itself. Running it in that state shortens its life.
There is also the environmental angle. If the cause is a leak, every hour of running can push more refrigerant into the atmosphere. Refrigerants are potent greenhouse gases, which is one reason handling them is regulated.
Switch the unit off and leave it until a technician has checked it. If you notice a strong chemical smell or hissing sound, keep people away from the area and mention it when you book.
Australian Conditions
Do Australian Conditions Make Refrigerant Leaks More Likely?
Coastal corrosion is a well known contributor. Salt air attacks copper pipes, brazed joints and aluminium coil fins. Over years, pinhole leaks can develop, particularly on units close to the ocean in Sydney’s eastern suburbs, the Gold Coast, Perth’s coastal strip and Adelaide’s beachside suburbs.
Heat and vibration play their part too. In long hot summers in Perth and Adelaide, outdoor units run for hours at high load. Vibration slowly loosens flare joints and rubs pipes against brackets or walls. Without proper support and insulation, wear points can become leaks.
Brisbane’s storms bring another risk. Falling branches and wind blown debris can damage exposed pipework. In established Melbourne suburbs, renovations and garden work sometimes nick pipes running along walls or through garden beds.
New Systems
Why Might F91 Appear on a New Installation?
F91 on a brand new or recently relocated system usually points to installation details rather than worn parts. That changes who you should call first.
Valves left closed
Outdoor units ship with their valves closed. If they were not fully opened after installation, refrigerant cannot flow freely.
Long pipe runs
Systems with longer pipe runs than the factory charge allows need extra refrigerant. Missing that step leaves the system short.
Poor flare joints
A flare made in a hurry or tightened incorrectly can leak from the first day.
If your system is new, contact the installer. Installation defects are normally their responsibility to correct.
The Regas Question
Why Is a Simple Regas Not Enough for F91?
It can be tempting to ask for a quick top up and move on. Unfortunately, that rarely solves the problem for long, and there are good reasons a careful technician resists it.
The leak remains
Gas added to a leaking system escapes again. The code returns, sometimes within weeks, and you pay twice.
Moisture and air
A leak can let air and moisture into the system. Without a proper vacuum, these contaminants stay and harm the compressor.
Charge accuracy
Panasonic inverters need a precise charge. Topping up without recovering and weighing the charge risks overfilling or underfilling.
Environmental duty
Repeatedly topping up a known leak releases refrigerant to the atmosphere, which licensed technicians are obliged to minimise.
Booking Details
What Information Speeds Up an F91 Repair?
Refrigerant jobs involve specialist equipment and sometimes a specific refrigerant. Sharing the right details lets the technician arrive prepared.
- The model numbers from both the indoor and outdoor units.
- The refrigerant type printed on the outdoor unit label, such as R32 or R410A.
- The approximate age of the system and when it was installed.
- Any history of previous regassing or leak repairs.
- How long the pipe run is between the units, if you know.
- Where the outdoor unit sits and how to reach it.
With this information, the technician can bring the right refrigerant, gauges and parts, which reduces the chance of a second visit.
Prevention
Can You Prevent Refrigerant Problems?
Not every leak can be avoided, but care and maintenance lower the risk considerably.
Protect the pipework
Keep pipe insulation intact and pipes well supported. Replace insulation damaged by sun, birds or pests.
Service regularly
A technician checks joints, valve caps and performance during routine servicing, spotting slow leaks early.
Act on early signs
Weakening performance, frost or hissing deserve a prompt check rather than waiting for a code.
Related Codes
Which Codes Often Appear Alongside F91?
Refrigerant problems ripple through the system, so other protection codes sometimes appear in memory as well.
Get Help
How Do You Book a Licensed Technician for F91?
Call us with the code, your suburb and both model numbers. Let us know if the system is new, recently relocated or previously regassed. We arrange licensed technicians in Sydney, Melbourne, Brisbane, Perth and Adelaide.
Panasonic pages for each city: Sydney, Melbourne, Brisbane, Perth and Adelaide. General repairs: Sydney, Melbourne, Brisbane, Perth and Adelaide.
Rapid Air Cooling is an independent booking business, not Panasonic, with no manufacturer authorisation. Read about our air conditioning service Australia wide.
Good to Know
What Else Is Useful to Know About F91?
Open more detail
Panasonic detection logic for F91 generally requires the abnormal condition to repeat within a set period before the code locks in. That is why a system may cut out a few times before F91 finally appears.
Older Panasonic systems may use R410A refrigerant, while many newer ones use R32. The technician needs to know which refrigerant your system uses, which is printed on the outdoor unit label.
Very old systems running obsolete refrigerants raise a different question. Parts and refrigerant may be scarce, so the technician may discuss whether repair or replacement makes more sense.
Leak repairs vary widely. A loose flare nut may be fixed in minutes, while a leak inside a coil may need the coil replaced. The technician will explain the options once the leak is found.
Finally, after a leak repair, ask for the job details in writing. A record of the leak location and the amount of refrigerant charged is useful if problems arise later.
It also helps to understand that refrigerant leaks can be intermittent. Some leaks only open up when pipes expand in the heat or vibrate under heavy load. A system may hold pressure on a cool morning, then lose gas slowly through a hot afternoon. Experienced technicians allow for this by testing under pressure and, where needed, checking again after a period of operation.
Finally, if you rent, tell your property manager about F91 promptly. Refrigerant repairs are a landlord responsibility in most tenancies, and early reporting avoids a long wait in peak season. Share the code and any symptoms you noticed in writing.
Questions
Frequently Asked Questions
Does F91 always mean a gas leak?
Not always. A partly closed valve, an incorrect initial charge or a stuck expansion valve can also cause it. A leak is the usual cause on older systems.
Can I just get the system regassed?
Regassing without finding the leak is a short term fix. The gas escapes again and the code returns. Leak repair should come first.
Why did F91 appear after my system was moved?
Relocation involves disconnecting and reconnecting pipes. A poor flare, incorrect charge or valve not fully opened can follow. Contact whoever moved it.
Can I see a refrigerant leak?
Sometimes. Oily residue at joints is one clue. Most leaks, though, are too small to see and need detection equipment.
Is it dangerous to be near a unit with F91?
A small leak in a well ventilated area is not usually a hazard to people. Avoid touching pipes, keep naked flames away and let a technician assess it.
Will my compressor be damaged?
The protection is there to prevent that. Stopping the system promptly when F91 appears gives the compressor the best chance of staying healthy.
How long does an F91 repair take?
A valve issue can be fixed quickly. Leak finding, repair, vacuum and recharge take longer, and parts may be needed for larger repairs.
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Reviewed by AC repair and service specialist on 22 October 2026. How we write our articles