🔧 AC Not Turning On? Complete Troubleshooting Guide for Power, Remote & PCB Issues
Problem Overview
If your air conditioner completely refuses to turn on—no lights, no beeps, no display—the issue could be with the power supply, remote control, main PCB, or internal safety mechanisms. This guide covers all common causes and fixes for both split and window ACs.
Safety First
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Turn off AC breaker: Switch off the dedicated AC circuit breaker before checking electrical connections to prevent shock hazards.
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Don't open outdoor unit cover: Never open the outdoor unit cover without proper training—it contains high voltage capacitors that can hold charge even when power is off.
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Warranty concerns: Opening the indoor unit or tampering with components may void your warranty. Check warranty status before DIY troubleshooting.
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Wait 5 minutes: After power cycling, always wait 5 minutes before turning the AC back on to protect the compressor.
🔍 Quick Checks ⏱️ 2-5 minutes
1 Check Main Power Supply
Verify AC breaker is ON, check if other appliances on same circuit work, and look for tripped MCB/ELCB.
2 Test Remote Control
Replace batteries, check for physical damage, use phone camera to see if IR signal transmits (LED should glow on camera screen).
3 Inspect Indoor Unit Display
Look for any indicator lights or error codes on the indoor unit. Complete darkness indicates power supply issue.
4 Check Emergency/Manual Button
Most split ACs have a manual ON/OFF button inside the front panel. Try this to rule out remote issues.
💡 Common Causes → Solutions
Problem
No power to AC—MCB tripped or power cut
Solution
Check main electrical panel, reset tripped MCB. If it trips again immediately, call an electrician—may indicate short circuit.
Problem
Remote control dead or not communicating
Solution
Replace batteries (use good quality alkaline), clean battery contacts with dry cloth, check IR LED with phone camera. If remote is faulty, use manual button or buy universal AC remote.
Problem
Blown fuse on indoor unit PCB
Solution
Open front panel, locate small glass/ceramic fuse on PCB (usually 5A). Replace if blown. Common in areas with voltage fluctuations—install stabilizer.
Problem
Transformer failure on PCB (no power to controls)
Solution
PCB transformer converts 220V to 12V/5V for controls. If burnt (smell/visible damage), requires PCB replacement by technician. Cost: ₹2,000-₹5,000.
Problem
Loose or disconnected wire connections
Solution
With power OFF, check terminal block connections on indoor unit. Tighten any loose wires. Common after installation or service work.
Problem
Voltage too low (under 180V) or high (over 260V)
Solution
Most ACs have built-in voltage protection. Install a dedicated AC stabilizer (₹2,500-₹6,000) if your area has frequent voltage fluctuations.
Problem
Safety switch/float switch triggered (window AC)
Solution
Window ACs have overflow safety switch. Empty drain pan, check drain hole isn't blocked. Reset the switch if accessible.
Problem
Compressor overload protection activated
Solution
Turn off AC for 30 minutes to cool down. If repeatedly activates, compressor may be failing—call technician for diagnosis.
🛠️ Step-by-Step DIY Troubleshooting
Verify Main Power Supply
• Check if AC circuit breaker in main electrical panel is ON
• Test the outlet with another appliance to confirm power
• Look for any area-wide power cuts or voltage issues
• If MCB keeps tripping, STOP—this indicates a serious electrical fault
Test Remote Control Thoroughly
• Replace batteries with fresh alkaline cells (not cheap carbon-zinc)
• Clean battery contacts with pencil eraser to remove corrosion
• Point remote at phone camera and press any button—IR LED should flash on screen
• Try universal AC remote app on smartphone as backup
Use Manual Emergency Button
• Open the front panel/filter cover of indoor unit
• Look for small button labeled "ON/OFF", "AUTO", or "EMERGENCY"
• Press and hold for 3 seconds—AC should start in auto mode
• If AC starts with manual button but not remote, replace remote
Inspect PCB Fuse (Split AC)
• Turn OFF main AC breaker for safety
• Remove front cover and carefully open control box cover
• Locate small glass tube fuse (usually 3A or 5A) on PCB
• If black/broken inside, replace with exact same rating
• Reassemble and test
Check Wiring Connections
• With power OFF, check terminal block on indoor unit
• Look for loose, burnt, or disconnected wires
• Tighten all screw terminals gently (don't over-tighten)
• Check for any visible burn marks or melted insulation
Reset AC Completely (Power Cycle)
• Turn OFF AC from remote/manual button
• Switch OFF circuit breaker and wait 5 minutes
• Switch breaker back ON
• Wait 1 minute, then try turning AC on
• This resets all electronics and can clear glitches
Check Voltage Levels (If Available)
• Use multimeter to measure voltage at AC outlet
• Should be between 210-240V for Indian ACs
• Below 180V or above 260V can prevent startup
• If voltage issues persist, install stabilizer
Final Diagnosis: PCB or Compressor Issue
If all above steps fail and you have confirmed power supply is good:
• PCB transformer or main board may be faulty (₹2,000-₹5,000 repair)
• Compressor protection circuit may be permanently triggered
• Outdoor unit PCB failure (less common)
• Professional diagnosis required with multimeter testing
📞 When to Call a Professional
⚡ Electrical & Safety Issues
- • MCB trips repeatedly when AC is turned on
- • Burning smell from indoor or outdoor unit
- • Sparking or buzzing sounds from electrical connections
- • Voltage fluctuation issues affecting multiple appliances
- • Any visible damage to wiring or components
🔧 Component Failures
- • PCB transformer failure (requires replacement)
- • Main control board not responding
- • Compressor overload protection permanently triggered
- • Complex wiring issues or connection problems
- • AC still under warranty (DIY may void it)
💰 Expected Repair Costs (2025 India)
PCB Replacement: ₹3,000-₹7,000
Fuse Replacement: ₹200-₹500
Diagnostic Charges: ₹300-₹800
🔍 Brand-Specific Quick Fixes
Daikin ACs
Check for "U4" or "U5" error codes on display—indicates communication failure between indoor and outdoor units. Power cycle usually fixes this.
LG ACs
LG units have "CH" error for communication issues. Remove batteries from remote for 30 seconds, then try. Also check for "Clean Filter" light blocking operation.
Samsung ACs
Samsung ACs often have self-diagnostic mode—hold TEMP+ and TEMP- for 5 seconds to see error codes. E5 = compressor overload protection.
Voltas/Blue Star
Check if timer is accidentally set. Blinking power LED often indicates timer mode—press "Timer" button repeatedly to cancel.
🛡️ Preventive Care & Maintenance
Monthly Checks
Clean indoor filters, check for any unusual sounds, test remote battery levels, inspect for water leaks
Annual Service
Professional deep cleaning, gas pressure check, PCB inspection, all connection tightening, stabilizer check
Warning Signs
Delayed startup, flickering lights when AC starts, warm air instead of cool, unusual sounds from outdoor unit
💡 Essential Prevention Tips:
- • Install stabilizer: Protects against voltage fluctuations (mandatory in areas with unstable power)
- • Use dedicated circuit: Don't share AC circuit with other heavy appliances
- • Proper earthing: Ensure AC has proper grounding to prevent component damage
- • Regular cleaning: Dusty PCBs can cause shorts—schedule professional cleaning annually
- • Surge protection: Use spike guards during monsoons to protect electronics
- • Off-season care: Run AC for 30 minutes monthly even in winter to keep compressor lubricated
❓ Frequently Asked Questions
Q1: My AC was working fine yesterday, now completely dead. What happened?
Most likely causes: (1) Power supply issue—check MCB/breaker, (2) Remote battery died, (3) PCB fuse blown due to voltage spike. Start with quick checks before assuming major failure.
Q2: Indoor unit has lights on but won't respond to remote. What's wrong?
If display/indicator lights are on, power supply is fine. Issue is either: (1) Dead remote—replace batteries and test with phone camera, (2) IR receiver damaged on indoor unit, (3) Remote unpaired from unit. Try manual button to confirm.
Q3: How can I test if my remote is working without a phone camera?
Alternative methods: (1) Point remote at AM radio—should hear clicking/interference, (2) Try in completely dark room—some people can see faint red glow from IR LED, (3) Swap with neighbor's same-brand remote to test. Phone camera is most reliable though.
Q4: AC PCB fuse keeps blowing repeatedly. What's the cause?
Recurring fuse blow indicates underlying electrical issue: (1) Voltage surges/fluctuations—install stabilizer, (2) Short circuit in wiring or PCB component, (3) Compressor overload, (4) Damaged capacitor. Don't keep replacing fuse—find root cause or call technician.
Q5: Is it safe to run AC without stabilizer in India?
Depends on your area's power quality. Modern inverter ACs (2020+) have wider voltage range (150-270V) and may not need stabilizer in stable supply areas. Older ACs or areas with frequent fluctuations MUST have stabilizer to prevent PCB/compressor damage. When in doubt, install one—costs ₹2,500-₹6,000, saves expensive repairs.
Q6: Manual button starts AC but remote doesn't work. Need new remote?
Yes, if manual button works but remote doesn't (after battery replacement and IR test), remote is faulty. Options: (1) Buy original replacement (₹600-₹1,500), (2) Universal AC remote (₹300-₹800), (3) Smartphone IR blaster apps if phone supports it. Original remote recommended for full functionality.
Q7: How long should I wait after power cut before turning AC back on?
ALWAYS wait 5 minutes after power restoration before turning on AC. This allows: (1) Compressor pressure to equalize preventing strain on startup, (2) Voltage to stabilize after restoration, (3) Capacitors to discharge safely. Immediate restart after power cut is leading cause of compressor damage.
Q8: AC worked fine last summer, won't start this year. Stored improperly?
Common after long off-season: (1) Remote batteries leaked/died during storage, (2) Dust/moisture on PCB causing issues, (3) Compressor oil settled—normal, just needs time, (4) Rodent damage to wiring (if outdoor). Try power cycle, replace remote batteries, run for few minutes in fan mode first to warm up compressor.
⚠️ Disclaimer: This troubleshooting guide is for informational purposes only. Always prioritize safety when dealing with electrical appliances. If you're unsure about any step, or if the AC is under warranty, contact authorized service centers. Incorrect repairs can cause equipment damage, fire hazards, or void warranty. When in doubt, call a professional technician.
Important Safety Reminder
If you're not comfortable with any step, or if the problem persists after trying these solutions, please contact a qualified technician. Safety should always be your first priority when dealing with electrical appliances.
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