P1 / PC01 DC Over Voltage or Low Voltage Protection

P1 / PC01 DC Over Voltage or Low Voltage Protection

Troubleshooting Guide – Service Technicians)

P1 ya PC01 Error Code tab display hota hai jab outdoor inverter PCB ko DC Bus Voltage normal range se zyada (Over Voltage) ya kam (Low Voltage) milta hai. Compressor aur IPM (Intelligent Power Module) ko damage se bachane ke liye outdoor PCB compressor ko turant stop kar deta hai.

1. Low ya High AC Input Voltage

Sabse pehle outdoor unit ki incoming AC supply voltage check karein.

Check

  • Outdoor terminal par AC Voltage measure karein.
  • Voltage manufacturer ki specified range ke andar honi chahiye.
  • Loose ya burnt terminal check karein.

Solution

  • Incoming power supply ko correct karein.
  • Loose wiring ko tighten karein.
  • Burnt cable ya terminal replace karein.
  • Agar voltage frequently fluctuate hoti hai to suitable voltage stabilizer use karein.

2. DC Bus Voltage Check

Outdoor PCB ke main capacitor par DC Voltage measure karein.

Normal Value

230 VAC Input → Approximately 310–340 VDC

Agar DC Voltage bahut kam ya bahut zyada ho to:

Check

  • Bridge Rectifier
  • Main Filter Capacitor
  • PFC Circuit (agar model mein available ho)

Solution

  • Faulty component replace karein.
  • Zarurat padne par Outdoor PCB replace karein.

3. Main Electrolytic Capacitor Fault

Weak ya damaged capacitor DC voltage ko unstable bana deta hai.

Check

  • Capacitor phoola hua ho
  • Oil leakage
  • Low capacitance
  • High ESR

Solution

  • Same value aur voltage rating ka naya capacitor replace karein.

4. Bridge Rectifier Fault

Bridge Rectifier AC ko DC mein convert karta hai.

Check

  • Multimeter ke Diode Mode se test karein.
  • Short ya Open condition check karein.

Solution

  • Faulty Bridge Rectifier replace karein.

5. PFC Circuit Failure (Applicable Models)

Kuch inverter models mein Power Factor Correction (PFC) circuit hota hai jo DC Bus Voltage ko stable rakhta hai.

Check

  • PFC Inductor
  • PFC MOSFET
  • PFC Diode
  • PFC Controller IC

Solution

  • Faulty PFC components replace karein.

6. Loose ya Burnt Power Wiring

Loose connection ki wajah se voltage drop hota hai.

Check

  • Terminal Block
  • Power Cable
  • Indoor to Outdoor Wiring
  • Burnt Connectors

Solution

  • Loose connection tighten karein.
  • Damaged cable ya connector replace karein.

7. Compressor Overload

Agar compressor zyada current draw karta hai to DC Bus Voltage collapse ho sakta hai.

Check

  • Compressor winding resistance (U-V, V-W, W-U)
  • Sabhi winding resistance lagbhag equal honi chahiye.
  • Compressor insulation Earth se check karein.
  • Compressor running current measure karein.

Solution

  • Agar compressor winding short ya earth ho to compressor replace karein.

8. IPM (Intelligent Power Module) Fault

Damaged IPM DC Bus Voltage ko abnormal bana sakta hai.

Symptoms

  • Compressor start nahi hota.
  • Outdoor PCB turant trip ho jata hai.
  • PCB par burn marks ho sakte hain.

Solution

  • IPM Module ya Outdoor PCB replace karein.

9. Outdoor PCB Fault

PCB ke andar voltage sensing circuit kharab ho sakta hai.

Possible Faults

  • DC Voltage Sensing Circuit
  • ADC Circuit
  • Voltage Divider Resistors
  • Controller IC

Solution

  • Outdoor PCB repair ya replace karein.

10. Power Supply Fluctuation

Bar-bar voltage low ya high hone se P1 ya PC01 error repeatedly aa sakta hai.

Solution

  • Utility supply check karein.
  • Suitable Voltage Stabilizer install karein.

Recommended Troubleshooting Sequence

Step 1

Incoming AC Voltage check karein.

Step 2

Power wiring aur terminal inspect karein.

Step 3

Main capacitor par DC Bus Voltage measure karein.

Normal Value : 310–340 VDC

Step 4

Main Filter Capacitor check karein.

Step 5

Bridge Rectifier test karein.

Step 6

PFC Circuit inspect karein (Applicable Models).

Step 7

Compressor winding aur insulation test karein.

Step 8

IPM Module inspect karein.

Step 9

Sab kuch normal hone par Outdoor PCB replace karein.

Safety Precautions

  • Service se pehle mains power OFF karein.
  • PCB touch karne se pehle DC Bus Capacitor discharge karein.
  • Insulated tools aur PPE ka use karein.
  • Main capacitor terminals ko kabhi short na karein.
  • PCB handle karne se pehle ensure karein ki DC Voltage safe level par aa chuka hai.

Common Symptoms

Symptom Possible Cause
P1 Error DC Bus Over Voltage ya Low Voltage
PC01 Error DC Voltage Protection Active
Compressor Start Nahi Hota DC Voltage Abnormal
Outdoor Unit Turant Trip Ho Jata Hai IPM ya PCB Fault
Bar-Bar P1 Error Aata Hai Power Fluctuation ya Capacitor Fault
Outdoor PCB Dead Bridge Rectifier ya PCB Damage
DC Voltage Stable Nahi Hai Capacitor, PFC Circuit ya Bridge Rectifier Fault

Service Technician Tip

Outdoor PCB replace karne se pehle hamesha AC Input Voltage, DC Bus Voltage (310–340 VDC), Bridge Rectifier, Main Filter Capacitor, PFC Circuit, aur Compressor ki condition ko verify karein. Agar root cause identify kiye bina PCB replace kar di jaati hai, to nayi PCB bhi dobara damage ho sakti hai.



Troubleshooting Guide (For Service Technicians)

The P1 or PC01 error code indicates that the inverter outdoor PCB has detected an abnormal DC bus voltage. The voltage may be too high (Over Voltage) or too low (Under Voltage). To protect the compressor and IPM (Intelligent Power Module), the system stops compressor operation.

Possible Causes

1. Low or High AC Input Voltage

The outdoor PCB converts the AC mains into DC voltage. If the input supply is outside the specified range, the DC bus voltage also becomes abnormal.

Check

  • Measure the AC supply voltage at the outdoor unit.
  • Verify the voltage remains within the manufacturer's specified operating range.
  • Inspect terminals for loose or burnt connections.

Solution

  • Correct the incoming power supply.
  • Tighten loose wiring.
  • Replace damaged cables or terminals.
  • Install a voltage stabilizer if frequent voltage fluctuations occur.

2. Abnormal DC Bus Voltage

Measure the voltage across the main electrolytic capacitor.

Typical values:

  • 230 VAC Input → Approximately 310–340 VDC

If the voltage is significantly higher or lower than normal:

Check:

  • Rectifier bridge
  • Main filter capacitor
  • PFC (Power Factor Correction) circuit, if equipped

Solution

  • Replace the defective electronic component.
  • Replace the outdoor PCB if necessary.

3. Faulty Main Electrolytic Capacitor

A weak or swollen capacitor causes unstable DC voltage.

Check

  • Bulging top
  • Oil leakage
  • Low capacitance
  • High ESR

Solution

  • Replace the capacitor with the same voltage and capacitance rating.

4. Defective Bridge Rectifier

A damaged bridge rectifier cannot properly convert AC to DC.

Check

  • Test each diode using the diode mode of a digital multimeter.
  • Check for short circuit or open circuit.

Solution

  • Replace the bridge rectifier.

5. PFC Circuit Failure (Applicable Models)

Some inverter models use a Power Factor Correction circuit to stabilize the DC bus voltage.

Check

  • PFC inductor
  • PFC MOSFET
  • PFC diode
  • PFC controller IC

Solution

  • Repair or replace the faulty PFC components.

6. Loose or Burnt Power Wiring

Loose terminals create voltage drops and unstable DC voltage.

Check

  • Terminal block
  • Power cable
  • Indoor-to-outdoor wiring
  • Burnt connectors

Solution

  • Tighten or replace damaged wiring and connectors.

7. Compressor Overload

A compressor drawing excessive current can cause the DC bus voltage to collapse.

Check

  • Compressor winding resistance (U–V, V–W, W–U should be nearly equal)
  • Insulation resistance to earth
  • Compressor current during startup

Solution

  • Replace the compressor if winding or insulation is faulty.

8. IPM (Intelligent Power Module) Failure

A shorted or damaged IPM may pull down the DC bus voltage.

Symptoms

  • Compressor does not start
  • Outdoor PCB trips immediately
  • Burn marks on PCB

Solution

  • Replace the IPM module or outdoor PCB.

9. Outdoor PCB Failure

Possible faults include:

  • Faulty DC voltage sensing circuit
  • Defective ADC circuit
  • Damaged control IC
  • Faulty voltage divider resistors

Solution

  • Repair or replace the outdoor PCB.

10. Power Supply Fluctuation

Frequent voltage dips or surges from the electrical supply may repeatedly trigger protection.

Solution

  • Check the utility supply.
  • Install an appropriately rated voltage stabilizer where recommended.

Recommended Troubleshooting Sequence

  1. Verify AC input voltage.
  2. Inspect all wiring and electrical connections.
  3. Measure the DC bus voltage (approximately 310–340 VDC).
  4. Check the main electrolytic capacitor.
  5. Test the bridge rectifier.
  6. Inspect the PFC circuit (if applicable).
  7. Test compressor windings and insulation.
  8. Check the IPM module.
  9. Replace the outdoor PCB if all other components are functioning correctly.

Safety Precautions

  • Disconnect the power supply before servicing.
  • Discharge the DC bus capacitor before touching the PCB.
  • Use insulated tools and appropriate PPE.
  • Never short the main capacitor terminals.
  • Verify that the DC voltage has fallen to a safe level before handling the board.

Common Symptoms

Symptom Possible Cause
P1 Error DC bus over-voltage or under-voltage
PC01 Error DC voltage protection activated
Compressor not starting Low or high DC voltage
Outdoor unit trips immediately IPM or PCB fault
Repeated P1 after restart Power supply fluctuation or faulty capacitor
Outdoor PCB dead Bridge rectifier or PCB damage
Unstable DC voltage Capacitor, PFC circuit, or rectifier failure

Service Tip

Before replacing the outdoor PCB, always verify the AC input voltage, DC bus voltage (310–340 VDC), bridge rectifier, main filter capacitor, PFC circuit (if available), and compressor condition. Replacing the PCB without identifying the root cause can result in repeated failures or damage to the new board.

Back to blog