Indoor fan blowing but outdoor silent: faulty starter relay

The indoor fan blew air, but the room stayed warm and the outdoor unit sat completely silent. A silent outdoor unit suggests a seized compressor. It also has cheaper causes worth ruling out first, so we traced the start path before condemning anything.

By Team Snowflake | Updated 28 Jul 2026

Case summary

Daikin Wall-mounted9 years oldHDBPunggol, Singapore

Concern: A seized compressor was the fear, which would mean replacing the whole outdoor unit.
Found: starter relay fault in the outdoor unit
Key check: Checked the outdoor start path and starter relay response before condemning major parts
Result: Cooling returned to normal on the first cycle. The compressor and every other outdoor part stayed in place, with no further work needed. The owner avoided a full outdoor unit replacement, since the only failed item was a low-cost relay rather than the compressor first suspected.

What we were told

The indoor fan is blowing but the room stays warm, and the outdoor unit is completely silent. I am worried this means the compressor has gone. I wanted a second opinion before committing to a replacement.

What we checked

A silent outdoor unit has a short list of causes. We worked along the start path from the control signal down to the compressor, ruling out each link in turn.

The indoor unit was sending the start command correctly. The communication link tested normal.
Incoming power was present at the outdoor connection point, so the mains supply was not the problem.
The starter relay clicked in when the command arrived, but its contacts were pitted and burnt.
No power reached the compressor terminals despite the relay moving. The worn contacts were not passing current.
The compressor itself tested healthy electrically, with no short to ground.

What we found

Each time the system calls for cooling, the starter relay closes a set of contacts to feed mains power to the compressor. Over nine years of switching, those contacts slowly burnt and pitted until they could no longer pass power cleanly. The relay still pulled in when the command arrived, but the damaged faces blocked the current. From outside, the unit looked dead. No hum, no fan, no sound at all. Yet the compressor, run capacitor, control board, and fan motor all tested healthy. The unit was fine. The start path was simply broken at one relay.

What fixed it

We fitted a matching starter relay for this Daikin model and confirmed a clean power path to the compressor. The outdoor unit started on the first command without hesitation. We ran the system through a full cycle and checked that the compressor and refrigerant circuit were working normally after the idle period.

Outcome

Cooling returned to normal on the first cycle. The compressor and every other outdoor part stayed in place, with no further work needed. The owner avoided a full outdoor unit replacement, since the only failed item was a low-cost relay rather than the compressor first suspected.

What this case teaches us

A silent outdoor unit is not always a dead compressor

The compressor only runs once mains power reaches it. A worn relay can block that power while every major part stays healthy.
Test the start path before quoting a compressor. The relay, the wiring, and the incoming supply are cheap to check and cheap to fix.
A confident replacement quote is worth a second opinion. Here the fault was a single relay, not the outdoor unit.

Questions this case answers

Indoor fan blowing but outdoor unit silent: what does that mean?

It means the start command is not reaching the compressor, and several cheap links sit in that path. In this Punggol flat the indoor unit was sending the command correctly and mains power was present at the outdoor connection point, yet no power reached the compressor terminals. A worn starter relay was blocking it.

What is a starter relay and how does it fail?

It is the switch that feeds mains power to the compressor whenever the system calls for cooling. Its contact faces burn and pit slowly across years of switching until they can no longer pass current cleanly. The relay here still clicked in on command, which is what makes the fault easy to miss. Movement is not the same as conduction.

Is a silent outdoor unit always a seized compressor?

No, and silence gives no clue on its own. A dead relay, a supply fault or a broken control link all produce the same nothing. On this Daikin the compressor tested healthy with no short to ground, and so did the run capacitor, control board and fan motor. One low-cost relay was the only failed item on the unit.

Can a relay be replaced without touching the compressor?

Yes, and that was the whole repair here. A matching starter relay went in and a clean power path to the compressor was confirmed. The outdoor unit started on the first command with no hesitation, and a full cooling cycle checked that the compressor and refrigerant circuit ran normally after the idle period.

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