Blue Star Air Conditioner
Blue Star AC L4 error
Current sensor (CT) fault
Try a reset once. If it comes back, a trained technician should repair it.
We found this meaning in only one secondary source. Confirm it with your user manual or brand customer care before any repair.
What it means
The control board is getting a wrong reading, or no reading, from the current sensor (CT). Usually the sensor, its wire or its plug is loose, damaged or has failed.
Common causes
- Loose or rusted sensor plug on the control board
- Sensor wire cut, pinched or bitten by rats
- Sensor has failed (open or short circuit)
- Less often, a fault on the control board
Try this at home first
Tick each step as you go
When to call a technician
If the code returns after a reset, a technician needs to test and usually replace the sensor. It is a common, low-cost repair.
Safety first
Always switch off at the wall socket or MCB before touching any part. Do not open the outdoor unit, control boards or gas pipes yourself — they carry high voltage and pressure.
Frequently asked questions
What does L4 mean on a Blue Star Air Conditioner?
Current sensor (CT) fault. The control board is getting a wrong reading, or no reading, from the current sensor (CT). Usually the sensor, its wire or its plug is loose, damaged or has failed.
Can I fix Blue Star Air Conditioner error L4 myself?
You can try a reset first: Switch off at the wall socket or MCB for 5 minutes, then restart. If the code returns, call a technician.
Is it safe to keep using the Air Conditioner with L4?
Avoid repeated restarts; running with this fault can cause more damage.
Other Blue Star AC codes
Same code on other brands
Sources
We write every explanation in our own words from these references.
- DigiRake Knowledge — Blue Star AC error codes
- ApplianceFaults.in — Blue Star air conditioner
- The Chill Spot — Blue Star AC error codes
- UniqRepair — Blue Star split AC error code list
- Republic World — Blue Star AC error codes list (inverter)
Last checked: 2026-10-20