Aircon cuts out every afternoon: trapped heat in outdoor alcove
A 7-year-old LG in Ang Mo Kio cooled fine every morning, then cut out around 2 to 4pm each afternoon. A failing compressor was the obvious fear. The cause was a new platform built above the outdoor unit, trapping heat in the alcove.
By Team Snowflake | Reviewed 3 Mar 2026
Case summary
LG Wall-mounted7 years oldHDBAng Mo Kio, Singapore
- Concern
- The worry was that the compressor was overheating from an internal fault, which would mean a major repair or a full replacement.
- Found
- Outdoor unit in a blocked alcove with new installation above trapping discharge airflow. Thermal protection tripping during peak afternoon heat
- Key check
- Visited during an afternoon cutout. Outdoor unit surface temperature was high. A new structure above it was trapping hot discharge air.
- Result
- The afternoon cutouts stopped once the platform clearance was raised. No parts were needed and the compressor was undamaged. Our parting advice was to keep clear space above the discharge grille before placing anything near the outdoor unit.
What we were told
The unit cut out every day between 2pm and 4pm for about a month, then restarted on its own after an hour. Mornings were fine. A previous technician suggested the compressor might be failing, but ran no tests. The trouble began around the time a new water heater platform was installed nearby.
What we checked
We booked the visit for the afternoon so we could watch the outdoor unit during the cutout window. Checking a time-of-day fault in the morning, when the unit runs fine, shows nothing. We arrived at 1:30pm and monitored the unit through the failure window.
The outdoor unit sat in a utility alcove walled on three sides, open only at the front.
A water heater platform had been built above the unit six weeks earlier, sitting close over the top discharge grille.
Air at the discharge grille measured well above the surrounding air, so the hot exhaust was being trapped instead of clearing upward.
The alcove itself was warmer than the open corridor a few steps away, which confirmed heat was pooling in the enclosed space.
A contact probe on the compressor read high but within the range for thermal protection, not mechanical damage. Power draw was normal while running.
What we found
The new platform sat too close above the unit's discharge grille. When the unit ran, hot exhaust hit the underside of the platform instead of clearing upward. It bounced back into the alcove and was pulled into the outdoor coil again. The unit was cooling its own hot exhaust instead of fresh air. Mornings were cool enough to cope. By early afternoon the trapped heat pushed it past its safety limit, so it cut out, cooled down, restarted, and tripped again.
What fixed it
We laid out the options. The platform could be raised for more clearance, opened up to let air pass through, or fitted with a duct to send hot air out of the alcove. Raising it was the simplest fix. We returned the next day and watched the unit through the afternoon peak. It ran without tripping once. No parts, refrigerant work, or compressor repair was needed.
Outcome
The afternoon cutouts stopped once the platform clearance was raised. No parts were needed and the compressor was undamaged. Our parting advice was to keep clear space above the discharge grille before placing anything near the outdoor unit.
What this case teaches us
A cutout that follows the clock points to heat, not a dying compressor
- The cutout happened only in afternoon heat, then cleared on its own. That timing points to thermal protection working, not a failing part.
- An outdoor unit needs clear space above it to vent hot air. Recent work nearby, like a new platform or shelf, can trap hot air against it.
- Tell us when the fault happens and what changed around the unit lately. Both narrow the cause faster than swapping parts.
Related reading
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