Marine Air Conditioner Will Not Start
No fan, no compressor, sometimes no display. Before this becomes an expensive phone call, it is worth working outward from the boat's own supply — a surprising share of dead units turn out to be dead circuits.
Won't start: First Checks
Not urgent. Is there 240 V at the boat at all? Check something else on the same circuit before you check anything on the unit.
Where this sits on the seawater loop
- Seacock
- Strainer
- Pump
- Condenser
- Evaporator
- Discharge
- Condensate
Electrical. Nothing here will be found by opening a strainer.Marine air conditioning is water-cooled, and that is what makes it different from a house. The full cutaway is in the guide.
Won't start: 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.
Confirm shore power is live and the main breaker is on.
Pedestals get switched off, cards run out, and leads get knocked out. Rule the free causes out first.
Check the unit's own breaker on the boat's panel.
A tripped breaker looks like a dead unit. Reset it once; if it trips again, read the tripping-the-breaker page instead of resetting it a second time.
Look at the controller display.
A blank display with power present usually means the controller has lost its supply or its data cable. A display showing a code means the unit is alive and refusing — read the code.
Check the controller's data cable at both ends.
These are usually plug-in and they work loose, especially where the run passes through a bulkhead that gets bumped.
Listen carefully for a click or a hum when you press start.
A click with nothing following points at a contactor or a start component. Complete silence points further upstream.
When to Stop and Call a Marine Technician
If there is power at the unit's terminals and it still does nothing, the fault is inside the machine. Opening a 240 V appliance on a vessel 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 Won't start
No supply, a tripped breaker, or a pulled lead
Free. Check it first every time.
A loose or damaged controller cable
Reseat both ends. Replace if the plug is corroded.
The controller in a standby or lockout mode
Read the manual's mode section. Seasonal lockouts catch people out.
A failed control board
Replacement, and a real cost — worth pricing against a new unit if the machine is old.
A failed start capacitor or contactor
Licensed work, but a cheap part.
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.