How long does a weld repair on an outdoor unit typically last?

It depends on the extent of surrounding corrosion. If the corroded area is isolated, a weld can last years. If the corrosion covers a broader section, new leaks may appear within months.

Is it worth trying a second weld if the first one failed?

Generally not if the pipe surface around the first weld is visibly corroded. A second weld on deteriorated pipe carries the same risk. Replacement becomes the more reliable option at that point.

Can the indoor units be kept when replacing the outdoor unit?

Yes, as long as the replacement outdoor unit is compatible with the existing indoor units. This is a common approach when the indoor units are still in good working condition.

LG Outdoor Unit Gas Leak Returns After Previous Weld Repair

Aircon case in Woodlands, Singapore: cooling loss traced to new refrigerant leak adjacent to previous weld on corroded pipe section after targeted diagnosis checks.

Case Details

Reported: My aircon was welded a couple of months ago for a gas leak. Cooling came back, but now the aircon is blowing warm again. The error light is on. I do not want to keep paying for the same repair.
Unit: LG · Wall-mounted · 5 years old
Location: HDB · Woodlands, Singapore

What We Checked

Refrigerant pressure was significantly below operating range.
Previous weld mark was visible on the outdoor unit gas line connection.
Green oxidation and surface pitting extended along the pipe on both sides of the weld.
Bubble test confirmed a new active leak roughly two centimetres from the old weld point.
LG error code CH35 was active, consistent with low-pressure protection.

The Diagnosis

The original weld sealed one leak point, but the underlying corrosion had spread along the pipe surface. The corroded area extended well beyond the weld. Heat from the welding process may have also stressed the adjacent pipe material. A new gap opened nearby where the pipe wall had thinned from oxidation. This is a common pattern when welding is applied to pipes where corrosion is not localised to a single point but covers a section of the connection area.

What Fixed It

We explained that welding the new leak was technically possible, but the corrosion pattern suggested the pipe section was broadly compromised. Another weld would carry the same risk of a third leak appearing nearby. We recommended replacing the outdoor unit to eliminate the corroded connections entirely. The indoor units were still in good condition and could be retained with a compatible replacement. The homeowner opted for outdoor unit replacement after weighing the risk of continued weld-and-recharge cycles.

The outdoor unit was replaced with a compatible LG unit. Existing indoor units were retained. The new connections were pressure-tested and the system recharged. Cooling has held steady with no further gas loss.

Why This Happens

Why welding corroded outdoor pipes often fails long term.

Welding seals the active leak point, but the surrounding pipe surface may already be weakened by the same corrosion.
Heat from welding can stress adjacent corroded areas, sometimes triggering new leaks nearby.
If the corrosion covers a broad section of the pipe, replacement is more reliable than repeated welding.
A single weld repair is worth attempting when the corrosion is isolated. When it spreads across the connection area, the odds shift toward replacement.

Same situation with your aircon?

Describe what’s happening. We’ll work out the likely cause and tell you the right next step.

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