Both were installed widely from the 1950s into the 1980s and both have documented histories of breakers failing to trip under fault. A breaker that does not trip is not a nuisance – it is the one safety device on that circuit not doing its job. There is no repair. If the label inside the door reads Federal Pacific Stab-Lok or Zinsco, replacement is the answer and it is worth doing before anything else on this list.

This is most common in homes built before about 1940. Pre-war construction — galvanized supply, cast iron drains, cloth-wrapped wiring, ungrounded circuits.

Related

• Two-prong outlets throughout the house
• Cloth-covered cable visible in the attic or basement
• Fuse panel, or a 60 amp service
• Fuse larger than the wire it protects
• Ceiling fan mounted to a standard light box
• Knob-and-tube still energised
• No GFCI protection anywhere in the house
• Breakers or fuses that are not labeled

Back to Electrical.

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Written by Jaylan Jones. I Like To Fix earns a referral fee when a call connects to a contractor. See our business-model disclosure.