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Garage electrical problem

954 Views 9 Replies 5 Participants Last post by  Bythepond88
The circuit breaker to my detached garage kept tripping. I traced the problem to an improper splice in the underground cable from the house to the garage. I fixed that with an underground approved splice kit. I double checked with a simple test light after the repair, and had power to the ends of the cable. But when I hooked the cable up to the garage wiring, nothing worked. I touched the test light to splices between the cable and garage wiring, and no light. Oddly enough, if I touch one lead of the test light to the common wire, there is a faint glow that goes out when I touch the other to the power wire.

The breaker does not trip, but there is no power when connected to the garage wire.

Apparently, there is a problem in the garage wiring (everything worked fine before the splice shorted out). Do these symptoms ring a bell with anyone. Any suggestions as to what to look for, other than to just disconnect the branch circuits in the garage one by one and track it down that way?
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Well, I started out by disconnecting wires, as Sparky said, but it seemed that every circuit with a switched load would drop the voltage to zero. Then, on a whim, I used the test light on an outlet, and it showed power, but when I plugged in a lamp, the lamp wouldn't work, either.

So I went back and disconnected the feed to the entire garage and hooked up the multimeter to the feed cable wires. I'd done that to begin with, and got a reading of 115v. This time, however, I kept the meter attached and watched the readings. Although they wandered up and down, on the whole, the readings were steadily decreasing from the initial 115v, to 100v by the time I stopped.

I went back to the breaker box, and took a reading from the power pole on the breaker to the bar where the common wires connect, and got a reading that hovered around 124v. So now I'm thinking that there's still a problem in the feed cable, maybe I didn't do the splice quite right.

Does that make sense?
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Update on the situation.

In answer to Sparky, the run from the breaker box to the garage is 40-50 feet, and is 12 gauge solid wire.

I recently moved to this house, and when I moved in, everything in the garage worked fine. The way I found the underground problem is that originally, the garage was wired to the same circuit as the back door light. As part of my troubleshooting when that light stopped working, I disconnected the garage from the circuit, and that circuit breaker stopped tripping.

I started digging up the cable to the garage, and found the bodged splice. I used an approved underground splice kit, and then added a new junction box in the crawlspace and added a separate circuit for the garage to the breaker box.

You are correct that the cable is compromised in addition to the bodged splice. After I noticed the voltage anomaly, I cut apart my new splice (I wasn't going to bury it again until I knew everything was working), and did another check at the end of the cable from the house, and found the same dropping voltage, albeit it wasn't dropping so quickly.

Further investigation is needed, and I will report back what I find.
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Re: Garage electrical problem - Solved!

Sorry for not posting back earlier. I climbed back into the crawlspace and discovered that there was indeed another splice and the common wire connection had come apart. I guess there was enough wire in the circuit for a microcurrent to get through, which is why I was getting a voltage reading. I'm also guessing that as that wire "filled up," it caused the voltage to slowly drop.

So I didn't have to undo my original underground splice, but that was a blessing in disguise, because I now realize that the cable running from that splice was regular NM, and not suitable for burying. (Up to that point, it was UF) So I replaced that run with proper UF cable.

Anyway, the lights are on again in the garage. Thank you all for all your help!

Next issue is that the cable from the house is only two conductor, with no ground wiring, but I'll start a new post regarding that.
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