Open or blown fuse

Take the fuse out and test it with a multimeter. A blown fuse reads open, with no continuity. Some inverters show a blown fuse as a fuse blown error on the device page of the user interface. Only check fuses on a de-energized unit. Turn the AC and DC switches off, wait for the inverter capacitors to discharge, and make sure there is no DC voltage or current before you open the fuse holders. A string wired with reversed polarity can blow the fuse when irradiance is high. The voltage across the blown fuse can reach twice Voc, which may stop the fuse from clearing properly and cause a fire. If all front-panel LEDs on a meter are dark, one possible cause is a blown power supply fuse. Connecting a test instrument to an energized circuit during a resistance test can blow the instrument's own fuse, so check that fuse before testing. Always replace a blown fuse with one of the same rating.

<!-- review notes

• sentence 2: support check: partial - u4 shows a 'fuse blown' error on the Inverter device page for PWRcell, but 'some inverters' is a generalization and the passage doesn't say the error indicates a blown fuse beyond the cause listed (it does list blown fuses as the cause).
• sentence 3: support check: partial - AC/DC off, 15-minute capacitor wait, and verifying absence of DC voltage and current are stated, but the passages don't say 'only check fuses on a de-energized unit' as a rule, though it is implied by the procedure.
• sentence 6: support check: partial - The passage says connecting to an energized circuit during the test blows the fuse and to check the fuse before testing, but it doesn't say explicitly it's the instrument's own fuse (implied by 'Testing the Fuse' in this manual). -->