Indoor fan blowing but outdoor silent: faulty starter relay
The indoor fan was blowing, but the room stayed warm. The outdoor unit was completely silent. Previous advice was that the compressor might have seized. We started with the start path instead.
By Team Snowflake | Reviewed 26 Feb 2026
Case summary
Daikin Wall-mounted9 years oldHDBPunggol, Singapore
- Concern
- Risk appeared to be a seized compressor requiring entire outdoor unit replacement.
- 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 all other outdoor components were retained without further work.
What we checked
A silent outdoor unit has a short list of causes. We worked through the start path from the control signal down to the compressor.
Indoor unit was sending the start command correctly. Communication link tested normal.
Incoming power was present at the outdoor wire connection point. Supply was not the issue.
starter starter relay energised when the start command was received, but contacts were pitted and not closing cleanly.
No power reached the compressor wire connections despite relay movement. broken internal path across the contact faces.
Compressor electrical checks were normal, with no short to ground.
What we found
Every time the system calls for cooling, the starter relay closes its contacts to connect mains power to the compressor. Over nine years and thousands of switching cycles, tiny electrical arcs formed across the contact surfaces each time the relay opened and closed. These arcs eroded the contact metal and left pitted, uneven surfaces. Eventually the pitting was severe enough that the contacts could no longer make a clean electrical connection when the starter relay energised. The starter relay pulled in mechanically, but the damaged contact faces could not pass power to the compressor. From the outside, the outdoor unit looked completely dead. No compressor hum, no fan spin, no sound at all. But the compressor motor internal motors, the run capacitor, the outdoor control board, and the fan motor were all tested and found to be in working condition. The unit was not dead, the power path to start it was broken at a single relay.
What fixed it
We replaced the starter relay with a matching unit for this Daikin model. After installation, we confirmed a clean power path to the compressor. The outdoor unit started on the first command without hesitation. We ran a full cooling cycle and checked that the compressor and refrigerant circuit were operating normally after the idle period.
Outcome
Cooling returned to normal on the first cycle. The compressor and all other outdoor components were retained without further work.
What this case teaches us
Trips and error codes need a step-by-step check
- Start with the pattern, not the worst-case quote. In this case, the useful clue was faulty starter relay.
- A trip or error code does not automatically mean a failed compressor or board. Rule out simple connection, sensor, or start-up faults before quoting major parts.
- Tell us when the error appears and what changed recently. Timing often identifies the first place to test.
Related reading
Ready to get started?
Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.