Quick answer
A mini-split that won't turn on has usually lost power or lost its remote signal. Check the breaker and the disconnect switch beside the outdoor unit first: on most brands the indoor head is fed from the outdoor unit. Then press the manual button under the front cover. If the head stays dead, the cause is a blown board fuse, a wiring fault, a tripped float switch or surge damage.
When your mini-split won't turn on, start by asking whether the head is dead or only ignoring you. A dead head shows no lights and makes no beep. A head that beeps, lights up and then does nothing has power and is reporting a fault, which is a separate problem covered under why a mini-split light is blinking. The checks below are for the dead one.
Check this yourself first
- Breaker: find the breaker for the mini-split in the panel, often a double-pole breaker labelled heat pump, A/C or ductless. Push it fully off, then on. Reset it once only.
- Outdoor disconnect: the grey box on the wall beside the outdoor unit. A switch type should be on; a pull-out type must be seated in the ON orientation, because the same handle fits upside down as OFF.
- Manual button: lift the front panel of the head. A small button, labelled ON/OFF, AUTO or Emergency, starts the unit without the remote. If it runs, the remote is the problem; see mini-split remote not working.
- Condensate pump or drain: if the head has a small pump, check whether its reservoir is full. A safety float switch cuts the unit off when the drain backs up, on purpose, so it cannot overflow down the wall.
- Patience in heating: at the start of a heating call the indoor fan waits until the coil is warm. Several minutes of a lit head with no air is normal.
Why the outdoor disconnect shuts off the indoor head
On most mini-split brands, power lands at the outdoor unit and travels to the indoor head through the same cable that carries the communication signal. There is no separate plug or breaker for the head. That is why a landscaper bumping the disconnect, or a breaker tripped by the outdoor unit, leaves the head on the wall completely dark.
It also means a problem in that cable takes down the whole system. The cable is a four-conductor run between the two units: two wires for power, a ground, and one that carries the signal, and manufacturers require it to run in one piece. A loose terminal screw, a hidden splice, water in the cable or a mouse in the line-set cover interrupts either the power or the conversation between the boards.
Blown fuses, float switches and surge damage
- Blown board fuse: both the indoor and outdoor circuit boards carry a small fuse. It blows to protect the board from a shorted fan motor, a pinched wire or a voltage spike. Swapping the fuse without finding the short blows the new one.
- Communication fault: the head may power up briefly and shut down, or the outdoor unit never answers. A technician checks the voltage on the signal conductor at both ends to find which board has stopped talking.
- Tripped float switch: clearing the drain or replacing the pump restores power. If the pump tank is full, why a condensate pump overflows explains the causes.
- Surge or lightning damage: inverter boards are sensitive electronics. A unit that died during a thunderstorm, or the moment power came back after an outage, often has a scorched board and sometimes a burnt smell at the outdoor unit.
- Lost settings after an outage: some models stay off when power returns until someone presses the remote.
None of the board work is a homeowner job. The outdoor unit runs on 240 volts on most installations, and its inverter capacitors hold a charge after the power is off. Work on the branch circuit itself, such as a failed breaker, belongs with a licensed electrician under ESA rules.
Call now if
- The breaker trips again as soon as you reset it.
- You smell burning at the head or the outdoor unit, or see scorch marks.
- Water is dripping from the head or running down the wall.
- The mini-split is the only heat in the room and it is below freezing outside.
What a no-power mini-split repair costs
A diagnostic visit runs $90–$150 and is folded into the repair if you go ahead. Most fixes for a dead mini-split, such as a reseated disconnect, a repaired cable termination, a cleared drain or a fuse replaced with its cause found, land in the $150–$800 band that covers most repairs. Control boards are typically $400–$800. The main inverter board on some outdoor units costs more than that, so that price is given in writing before the part is ordered.
The decision rule on an older system: when the unit is past 12 years old and the quote is for an outdoor inverter board, ask for a replacement price alongside it and compare the two.
ZK Mechanical services Mitsubishi, Fujitsu and Daikin ductless systems from the Burlington shop. Start with ductless mini-split service, or go straight to mini-split repair and send us the model number so we know which boards and fuses the unit takes.