About 3,200 electric customers in Hawaii Kai and the surrounding area were left in the dark for about 40 minutes Friday night after a glitch at a Hawaiian Electric Co. substation, a company spokesman said.

The outage happened when a substation failed to automatically switch over, said HECO spokesman Peter Rosegg. A HECO technician went to the substation and manually completed the switched over, restoring power about 8:20 p.m.

Rosegg said a crew will go out to the substation on Tuesday to find out why the automatic switch failed.