Photovoltaic combiner box has voltage but no current

Voltage without current in a PV combiner box usually indicates a broken or interrupted circuit, often caused by blown fuses, tripped breakers, or loose connections.Common Causes1. Blown Fuses or Tripped Breakers If a fuse inside the combiner box has blown or a DC circuit breaker has tripped, voltage may still be present on one side of the device, but current cannot flow to the inverter. This is a frequent cause when the system shows voltage but no current output. Fuses can blow due to overcurrent, short circuits, or lightning surges, while breakers may trip from overloads or age-related degradation . 2. Loose or Corroded Connections Loose terminals, poor contact, or corrosion at connection points can interrupt current flow even if voltage is measurable. Thermal cycling, vibration, or improper installation can degrade connections over time. Visual signs include discoloration, scorching, or corrosion on terminals and busbars . 3. Cable Breakage or Internal Conductor Faults Cables exposed to harsh outdoor conditions may develop insulation cracks or internal breaks. Even if voltage is present at the combiner box input, a broken conductor prevents current from reaching the output . 4. Faulty Surge Protection Devices (SPDs) If SPDs have failed due to lightning or overvoltage events, they may block current flow while still allowing voltage to appear across the combiner box terminals .Troubleshooting StepsSafety First: Always follow lockout/tagout procedures, wear arc-rated PPE, and verify zero energy before touching components .Visual Inspection: Check for loose connections, burnt marks, corrosion, or damaged cables.Check Fuses and Breakers: Measure continuity and replace blown fuses with the correct rating. Reset or replace faulty breakers.Measure Current: Use a DC clamp meter to check each string for current flow. Strings showing zero current indicate the location of the fault .Inspect SPDs: Verify SPD status indicators and replace any failed devices.Verify System Design: Ensure the combiner box and inverter ratings match the PV array output to prevent overcurrent issues .Key RecommendationsUse rated instruments such as a CAT III 1500V DC clamp meter and multimeter.Regularly maintain and clean the combiner box to prevent dust, water ingress, and thermal degradation.Replace components only with the correct type and rating to maintain system safety and efficiency . By systematically checking fuses, breakers, connections, and SPDs, you can identify why the combiner box shows voltage but no current and restore proper operation safely.