Heat Pump Repair in Portland & Southern Maine

Some frost on the outdoor coil during winter operation is completely normal — the unit runs a defrost cycle automatically to clear it. A thick, persistent ice buildup that doesn't clear on its own usually points to a failed defrost control, a refrigerant charge issue, or a fan motor that's stopped moving air across the coil. Continuing to run a heavily iced unit risks damaging the fan or compressor.

This is almost always one of three things: a refrigerant charge that's low from a slow leak, a dirty indoor or outdoor coil restricting heat transfer, or a system that was undersized or oversized for the space from the start. We check charge and airflow before assuming it's a sizing problem, since a leak is a repair and a sizing mismatch is a bigger conversation.

A unit that starts and stops in short bursts, or won't start at all, points at the electrical and control side — a failing capacitor, a tripped high- or low-pressure switch, or a control board fault. This is also where an undersized electrical circuit or a loose panel connection can masquerade as an equipment problem, which is one reason our electrical licensing matters on an HVAC call.

Mitsubishi Electric M-Series

Mitsubishi's MSZ-GX wall units flash a two-letter or two-digit code on the indoor unit and repeat it on a wired remote, if one's installed. The operating instructions publish the full list; these are the ones we see most:

Fujitsu Halcyon

Fujitsu's RLS2 wall units communicate a fault through a blink pattern on two LEDs — OPERATION and TIMER — which a wired remote (if installed) also shows as a two-digit code.

Daikin Aurora

Daikin's Aurora R-32 wall units run a self-diagnosis routine and show a code on the indoor display.

Carrier Ductless High-Wall Units

Carrier's 45MAHAQ ductless line displays an alphanumeric code on the indoor unit or wired controller when its self-diagnostics catch a problem.

LG: Look Up the Code by Model and Serial Number

Efficiency Maine's rebate list includes several LG ductless lines, single- and multi-zone alike, but LG breaks from how the other four manufacturers here handle documentation. There's no browsable manual archive — the lookup tool demands the exact model and serial number off the nameplate before it returns anything. Running that lookup didn't surface a usable fault-code table for us, so rather than guess at LG's codes, we're leaving them out entirely.

Practical takeaway if your LG unit throws a code or blinks a pattern: write down the code (or count the blinks) and copy the full model and serial number off the nameplate before calling. That's the pair of details LG support or a technician actually needs to look anything up.