Marine Air Conditioning Controller Fault Codes
Codes differ between makers and between generations of the same maker, so the honest advice is to read yours rather than trust a list on the internet. What does generalise is what the categories mean, and what you can usefully check before ringing anyone.
Fault code: First Checks
Depends what it is protecting against. Write the code down exactly, along with what the unit was doing at the time. That single note is worth more to a technician than any amount of description.
Where this sits on the seawater loop
- Seacock
- Strainer
- Pump
- Condenser
- Evaporator
- Discharge
- Condensate
Depends entirely on the code. A pressure trip points at the loop; a sensor or comms fault does not.Marine air conditioning is water-cooled, and that is what makes it different from a house. The full cutaway is in the guide.
Fault code: Diagnostic Steps
Work down it rather than picking the step that sounds most likely. The order is chosen so that the cheap, common causes are eliminated before the expensive, rare ones — which is also the order that stops you paying somebody to clean a strainer.
Record the code exactly and find your unit's manual.
The same characters mean different things on different makes, and sometimes on different model years of one make. Publishing a universal table would be actively harmful, which is why this site does not.
Note what the unit was doing when it appeared.
On start-up, after an hour, on switching to heat — each narrows it enormously, whatever the code says.
If it names high pressure, check the seawater side first.
That is the cause on Australian boats far more often than anything internal. There is a page for it.
If it names low pressure or a coil sensor, check airflow first.
Same logic in the other direction: the filter and the fan before the refrigerant.
Clear the code once, and see whether it returns.
A single event after a power interruption is different from a code that comes back every run. If it returns, stop clearing it and get it diagnosed.
When to Stop and Call a Marine Technician
Any code that resolves to a pressure, a sensor or a compressor fault leads into the refrigerant circuit, which is licensed work.
Handling refrigerant in Australia requires an ARCtick licence under the Ozone Protection and Synthetic Greenhouse Gas Management Regulations, and fixed 240 V work on a vessel is licensed under AS/NZS 3004.2. Both exist for good reasons. Everything above the line is yours; everything below it is not.
Possible Causes of Fault code
A pressure protection trip
Nearly always seawater flow or airflow. Check those first.
A communications fault between controller and unit
Reseat the data cable at both ends.
A sensor out of range
Sometimes a loose plug, sometimes a failed thermistor. Licensed work to confirm.
A supply-voltage fault
Marina pedestals do sag. Worth measuring before blaming the unit.
A control-board failure
Replacement. Price it against a new unit if the machine is old.
Ranked by how often each one is the answer on Australian boats, not by how often it appears in a service manual. The seawater side dominates this list because our water is warm, our marinas are full of growth, and the strainer is the part nobody opens.
Reporting This Marine Air Conditioning Fault
Tell us the boat, the unit if you know it, and what you found at each step above. We will tell you what we would check next, and whether it is worth a technician's call-out or a new machine. We do not charge for that and we will say if the honest answer is that the unit has had its life.