Garage/Low Floor Electrical Issue

Location
San Francisco, CA
Occupation
Electrician
Hey everyone,

Was troubleshooting an electrical issue where all the lighting/outlets and garage opener do not work ( well most - the water heater does work) and they have just three main circuit breakers and we did try to switch on and off the circuit breakers but it stayed on. We tried disconnecting everything and the lights/outlets and garage opener still wouldn't work. It is an old house and I told them they might have GFCI outlet hidden behind all those storage boxes the customer has in the garage and try locating that (customer moved in two years ago).

Customer mentioned her upstair tenant neighbor (it is a storage units) noticed the front lobby light just went off and things stopped working. So not exactly sure how we can pinpoint out this issue if the customer isn't able to locate any other hidden GFCI outlet or any other outlet.

Thanks in advance!
Accend
 
My first guess is a bad or improper feeder neutral, since you have 240v but not 120v. It's possible to have a good hot and a bad neutral and mistakenly think you have 'no' power at a receptacle or other outlet.

Plug an extension cord into a known-properly-working, non-GFCI-protected receptacle and use a tester (preferably solenoid) to test your circuits against the known-hot, -neutral, and -ground slots of the cord.
 
Thanks Larry for the quick reply. Is the voltage/neon tester the same as the solenoid tester? So if I connect an extension cord into a known working outlet on the first floor (there were a couple that did work near the water heater) and checking for known,-hot, neutral like you suggested, what are we looking for and what does it tell me how to troubleshoot further? Customer is concerned about cost too so would like to fix it asap without too many guessing :). thanks!
 
Is the voltage/neon tester the same as the solenoid tester?
No, but a neon tester is slightly better than a voltmeter for some troubleshooting.

Something that requires "real" power, like a small incandescent bulb, is better.

So if I connect an extension cord into a known working outlet on the first floor (there were a couple that did work near the water heater) and checking for known,-hot, neutral like you suggested, what are we looking for and what does it tell me how to troubleshoot further?
Think about what should appear between each two points you try.

Unplug everything first.

From the cord hot, the circuit hot should be either 0v or 240v, everything else should be 120v.

From the cord neutral and ground, the circuit hot should be 120v.

If a GFCI is open, on the load side of it, both the circuit hot and neutral will have 0v.
 
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