Cooling cuts under load: coastal corrosion at the outdoor terminal

A Marine Parade condo had already been topped up twice, but cooling still cut out under load. Near the coast, an intermittent cutout is not always the refrigerant circuit. The outdoor electrical connection needed checking before assuming the gas was fading again.

By Team Snowflake | Updated 28 Jul 2026

Case summary

Mitsubishi Electric Wall-mounted9 years oldCondoMarine Parade, Singapore

Concern: The resident expected another gas top-up because cooling seemed to fade during hot afternoons.
Found: Salt-corroded electrical terminal at the outdoor unit causing intermittent compressor cutout under load
Key check: Checked the outdoor electrical terminal and wiring connection before recommending another gas top-up
Result: The compressor ran through a full sustained load test without cutting out. The owner avoided another unneeded top-up, and the fault was traced to a connection that will now be checked at each service visit.

What we were told

The bedroom cooled normally most of the time, but the compressor cut out during long afternoon runs and restarted a few minutes later. The outdoor unit sat on a coastal-facing ledge, and the previous top-up had not stopped the pattern from returning.

What we checked

An intermittent cutout under load is a different case from steady weak cooling. We checked the refrigerant circuit first to rule out a fresh leak, then moved to the outdoor electrical connection, since a corroded contact can drop out under heavy load and reset once it cools. The goal was to find whether the fault sat in the gas circuit or the power path.

Refrigerant level tested normal, ruling out a fresh gas leak.
The compressor cut out repeatedly during a sustained cooling run.
The outdoor electrical terminal showed corrosion and a loose, pitted contact.
Cutouts stopped once the terminal contact was held firm by hand.

What we found

Salt air had corroded the electrical terminal feeding the outdoor unit. Under light load, the loose, pitted contact still passed enough power to run. Under sustained heavy load, resistance at the corroded point built up heat, and the connection dropped out, cutting the compressor as a protective response. The unit then cooled and reset, which is why the fault looked intermittent rather than constant. Refrigerant stayed at a normal level throughout, so the earlier top-up had never addressed the actual fault.

What fixed it

We advised cleaning the corroded terminal contacts, reworking the connection, and resealing the terminal against moisture, rather than any further gas work. The refrigerant circuit was left untouched since it tested normal. After the terminal was rebuilt, we ran the unit under a full sustained load to confirm the cutout did not return. We also advised checking this terminal at future servicing, since coastal air can corrode the same connection again over time.

Outcome

The compressor ran through a full sustained load test without cutting out. The owner avoided another unneeded top-up, and the fault was traced to a connection that will now be checked at each service visit.

What this case teaches us

Intermittent cutout near the coast can be a corroded terminal, not gas

Cooling that drops out under load, then returns, is a different pattern from a slow gas leak. It points to a connection fault, not a refrigerant one.
Coastal electrical terminals at the outdoor unit corrode just as fast as refrigerant joints. A cutout under load deserves a wiring check before another top-up.
Ask whether the outdoor electrical connection was inspected, not only the refrigerant circuit. A cleaned and resealed terminal can fix the pattern without adding gas.

Questions this case answers

Cooling keeps cutting out on hot afternoons then comes back: what is that?

A dropout-and-recover pattern behaves differently from a slow refrigerant loss. In this Marine Parade bedroom the compressor stopped during long afternoon runs and restarted minutes later. Refrigerant tested normal. The outdoor electrical terminal showed corrosion and a loose, pitted contact, and the cutouts stopped once that contact was held firm by hand.

Why did a gas top-up not fix the cooling problem?

Because refrigerant was never the fault. Level tested normal on this coastal-facing ledge unit, which meant earlier top-ups had added gas to a system that already had enough. Heat building at a corroded terminal under sustained load was cutting the compressor as a protective response. Cleaning, reworking and resealing that connection was what the evidence supported.

Does living near the sea affect aircon wiring as well as the pipes?

It does. Salt air works on electrical terminals at the outdoor unit at much the same rate as it works on refrigerant joints, and the damage is easy to miss because the unit still runs on light load. This terminal now sits on the checklist for future service visits at that flat.

How can I tell a gas problem from an electrical one?

Watch how the cooling fails. Gas loss makes a room steadily weaker and it stays that way. A connection fault drops out under heavy load, cools down, and comes back, so cooling seems fine most of the time. Describing that on-off behaviour is what moved this diagnosis to the power path.

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