Air-con runs but isn't cooling (electrical checks)
The unit runs (fan blows) but doesn't cool — from an electrical standpoint, checking whether the compressor/outdoor unit is actually being commanded and powered before handing to refrigeration.
Safety first
Isolate before electrical checks. Cooling performance often involves refrigerant — that's refrigeration-tech territory; here we confirm the electrical side.
Isolate, lock out / tag out, and prove dead before working unless a live test is specifically required, authorised, and carried out under proper supervision. Always follow local regulations, your site procedures, and the equipment manufacturer's documentation.
Apprentice mode
Full walk-through — the why, what readings mean, mistakes & safety.
Likely causes
Ranked from most to least likely.
- 1
Outdoor unit/compressor not running
Most likelyThe condenser/compressor isn't running, so no cooling — could be electrical (supply/contactor/cap) or refrigeration.
- 2
Mode/setpoint wrong on the controller
#2Set to fan-only, a too-high setpoint, or a schedule limiting it.
- 3
Outdoor fan/contactor/capacitor fault
#3A failed run capacitor, contactor, or outdoor fan motor stops the outdoor unit working.
- 4
Refrigerant/mechanical issue (hand off)
Least likelyLow refrigerant or a mechanical fault — refrigeration tech required.
Reports are saved on this device to reflect what you actually find.
Testing sequence
Work through one test at a time. Expected reading and what each result means.
On the tools? Job Mode shows one test at a time with thumb-sized buttons — your place and readings carry straight over.
Enter Job ModeCheck the controller mode/setpoint/schedule is actually calling for cooling.
Cooling mode, setpoint below room temp, not schedule-limited.
It's calling for cooling — check the outdoor unit electrically.
Wrong mode/setpoint/schedule — correct it.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
Aircon not cooling
→ step 2 - 2decision
Is the controller actually calling for cooling?
Yes→ step 3No→ step 4 - 3decision
Is the outdoor unit powered, commanded, and electrically healthy?
Yes→ step 5No→ step 6 - 4result
Correct mode/setpoint/schedule.
- 5result
Electrically OK but not cooling — refrigeration technician.
- 6result
Electrical fault (contactor/cap/fan/supply) — rectify.
Common mistakes apprentices make
- Not checking the controller is actually in cooling mode.
- Assuming refrigerant when a run capacitor/contactor has failed.
- Attempting refrigerant work without a licence.
- Not isolating before checking the outdoor unit.
When to stop & escalate
Once the electrical side is confirmed (unit powered and commanded), cooling-performance/refrigerant issues are for a licensed refrigeration technician.
If you're past your competence, authorisation, or the safe limits of the job — stop and hand it on. There's no fault worth getting hurt over.
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Related faults
Split-system air-con not running at all
A split-system (head unit + outdoor condenser) is completely dead — no response from the remote/controller — pointing at supply, isolator, controller, or the indoor PCB.
Air-con tripping the power
An air-con unit trips its breaker or safety switch — on start, when the compressor kicks in, or randomly — pointing at the compressor, an earth fault, or the supply/protection.
Ducted air-con system has no power / won't start
A ducted system (roof/cupboard fan unit + zones/controller) is dead or won't start — pointing at the dedicated supply/isolator, the controller, zone motors, or the unit's PCB.
Learn the theory
How the gear and circuits behind this fault actually work.