Garage Short Circuit?

symptoms 1. garage lights won't turn on 2. garage door opener won't go up/down 3. when light switch is off, garage opener sensors light up 4. when light switch is on (lights don't go on), sensors go off 5. Voltage tester shows 104 volts in all outlets in garage
what should I do (besides calling an electrician)?
the problem began soon after the first rains in 6 weeks
the power to the garage is underground conduit from the house, under the yard to the garage.
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MJR wrote:

10 to 1 you have a splice or screw connection which has gone bad in either the hot or neutral feed wires to the garage. It is not completely open, but has unusably high resistance.
At the very low current drawn by the garage door sensors there's still enough voltage (the 104 volts you measured) to let the sensors light up. Any load much heavier than that causes the voltage to collapse to near nothing. That's why trying to turn on a light makes the sensors go out.
Good luck finding it. If you are lucky and there are no splices or joints in the wires underground you may just find that there's a loose screw connection or wirenut on something like the circuit breaker feeding that line or maybe in a box in the garage where the underground wires split out to the various things using power in the garage.
Try using a light bulb with an appropriate socket and leads instead of your voltage tester. That'll give you a more realistic load to test with.
HTH,
Jeff
--
Jeffry Wisnia

(W1BSV + Brass Rat \'57 EE)
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Turn the circuit breaker(s) off, or pull the fuse(s).

Sounds like there's a leak in the conduit, and a break in the cable.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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MJR wrote:

For the moment, let's ignore that 104 Volts as I believe it is a red herring.
Go check the circuit breakers, Is one tripped? I suspect not. Now check out all your GFIs. One or more of them should be protecting your garage. They may be in the garage, kitchen bath or breaker box. It the test and reset button on each one.
If that gets you power, the 104V you found was only a very low amp induced current and you never would have been able to measure it without that digital meter you used.
--
Joseph Meehan

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Joseph Meehan wrote:

Joseph, I'm usually in agreement with you, but if there's enough current to light up the opener sensors I doubt that it's being provided by induced or capacitively coupled current. But, maybe if they are extremely low current devices there is a possibility of that happening.
Nothing to be lost by following the steps you describe, they are certainly the simplest thing to start with, but I'll still put my money on a high resistance joint somewhere.
That's assuming the OP's description and our understanding of what he means are correct, something that isn't always true on this newsgroup. <G>
Jeff
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Jeffry Wisnia

(W1BSV + Brass Rat \'57 EE)
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Many people, including some posters on this newsgroup, think that all electrical problems are a "short circuit" and have no concept as to what a short circuit is and what it would do. Their analytical skills and knowledge is just as accurate.

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EXT wrote:

Well, we can't expect everyone to be a qualified tech writer. I'm not one to rag on people who aren't skilled in every possible art, as long as they don't insist that they are when they're patently not. Sometimes trying to decode what a poster is really telling here can provide an interesting challenge.
I'd hate to have my internist chide me because I couldn't explain what I thought my ailment was using the proper clinical jargon.
OTOH, I pretty much agree with folks here who say, "Get a qualified electrician fast", when the OP seems too naive to get all the way up to speed through a few posts. Humans haven't evolved senses which let them see, hear or smell household electricity unless it's already started something frying or burning. The risks of immediate electrocution or subsequent incineration of innocent victims are pretty high. Apparant fools shouldn't be encouraged to rush in where angels dare to tread. (Sermon over.)
This all reminded me of when I used to repair radios & TVs in the vacuum toob days. I'd sometimes tell a customer that the problem I'd found in their equipment was "a loose disconnection" when I was pretty sure they'd never understand what I'd really done, even if I explained it a dozen times. <G>
Peace,
Jeff
--
Jeffry Wisnia

(W1BSV + Brass Rat \'57 EE)
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Jeff Wisnia wrote:

I suspect if they are lighting up the sensors, it is not just an induced current. Note that I did say IF that (resetting breakers and GFIs) ... Maybe I should have been more direct with my "IF" ;-)

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Joseph Meehan

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To all posters so far thanks. here are some additional comments
1. The circuit breaker never flipped to off by itself, I identified it and switched it off and on, to no avail and then switched it off for the day as a safety measure. 2. There are 3 wall outlets in the garage 2 with external GFI buttons, with both when I hit reset and hold it , I feel a subtle clicking noise, when I push the test button, the glow tester in the outlet goes off, when I release the test button the glow tester goes on. the reset button never "pops out" as I have seen with some other GFI outlets. 3. there are no other outlets or switches that I know of between the conduit leaving the house and that entering the garage. alowing with the hot and neutral wires, there is a 3 way switch bundle for an outside light on the garage, with switches in my kitchen and in the garage.
I think I will replace or check the circuit - in the interest of safety, I will have my wife actually swap it out :-)
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MJR wrote:

Try disconnecting the downstream wires at the GFIs. If things work normal (other than what would be out because you disconnected parts of the circuit, then I would guess you have a fault on the circuit you just disconnected.
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Joseph Meehan

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SUCCESS!
I tested the circuit breaker, no problem there
I tested the wire exiting the house, no problem there - tested with a bulb not a meter
I tested some outlets in the garage with a bulb, very dim light - orange glow was all I got.
I went back to the garage and tried to wrap my head around the wiring, where did it come into the garage from the underground conduit. after a couple days of an hour here and there, I decided it was time to break into the wall and find the junction from the house. I picked the wall, based on my understanding of the wiring, got out my saw, and then wifey came to look, she said "wait, isn't there something there? I checked and indeed there was a junction box hidden in the wall under a faceplate, covered and hidden behind a couple years worth of house discards that get stored in the garage. I removed the faceplate, tested the wires (always turning off the cicuit breaker before touching wires...) , same problem, dim bulb. Then, I saw it, a spare/unused wire in the bundle, what if I swapped the spare with the neutral or hot wire from the house? would it work? was just one wire damaged? In short yes, the neutral one was bad, now the spare (blue) is functioning as neutral, no wires to pull , no yard to dig up
life is good, thanks all
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MJR wrote:
That test result with the dim light, leads me to believe you have/had a floating neutral. I can't quite get into my head your wiring design, so I am not all that sure that you fixed the problem or just changed it. Floating neutrals can be dangerous. I once had a boss who burned down his prior photo studio because of a floating neutral.

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Joseph Meehan

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ldiddy had written this in response to http://www.thestuccocompany.com/maintenance/Re-Garage-Short-Circuit-22733-.htm : I read the short circuit thread and I don't know if that's my problem or not. My house electricity works, nothing in my garage works. Suggestions? Estimated costs?
------------------------------------- Jeff Wisnia wrote:

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The first thing to do is find the junction box in the garage, where the conduit comes into when it comes out of the ground, separate the feed wires from the load wires and test them for proper voltage. If you don't have it, check it at the other end of the conduit before it goes underground. This will at least give you some idea of where the problem is

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RBM wrote:

... and test again, with a modest load applied (100-watt trouble light or something similar).
I think the first guy who responded (Jeff) has it right.
If you don't have it,

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Do as others have said. Check the breakers and the connections in your main panel (in the house). This includes checking the neutral is connected in that box. Now, meter the voltage in there. If all is fine in there. Shut off the breaker to the garage, and go to the garage. Find where the wires enter the garage from the underground conduit. Open that box and find the nearest connection in there (most likely there are some wirenuts). Carefully check those wirenuts to be sure there are no loose or corroded connections. Take off the wirenuts, and separate the wires from the conduit from the garage wiring. Connect your meter. Go in the house and turn on the breaker, Go back to garage and read the voltage. It SHOULD be the same as in the house. Go back in house and shut off breaker. Go back to garage and connect a 100 watt light bulb AND your meter to those wires. (use aligator clips, or some other safe method to attach a light socket). Turn on the power. If lightbulb lights properly, your underground wiring should be ok, and there is another problem somewhere in the garage. If the light does not light up, or is too dim, you got a bad wire underground, and you need to replace that wire.
If there is conduit all the way from the house to the garage, you should be able to attach new wires to the old ones, twist them together, and tape them well so they do not separate under the ground. Now pull your new wires thru using the old ones. Use the same number or wires, same colors, and same gauge (or thicker). Once the new wires are pulled thru, reattach them as they were. By this time you should see where the problem is on the old wires.
Hope this helps.
PS. If the problem is elsewhere in the garage, open each and every box and check for bad connections.
I suspect you have a fried wire under the ground. I hope you got conduit all the way, or prepare to dig, and that is not fun !!!
Mark
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MJR wrote:

Using analog meter like Simpson 260? Measured voltage between hot and neutral, hot and ground? Is it on GFCI circuit?
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That sure sounds like an underground wiring problem. Not wires shorted to each other, but shorted to earth ground. 1. Try killing ALL power in the garage: physically unplug as much as you can, if it can't be unplugged, be sure it's OFF and not drawing any power (as in standby modes).
2. Do you see something closer to 110V at the panel in the garage? If so, something is drawing power between that panel and the main panel - as in, a ckt to gnd due to insulation compromise, whatever.
3. IF you're seeing something closer to 110Vac, then connect something in the garage that draws power. Perhaps a halogen light, or anything that will draw a few amps. Look at that same voltage again. If it's dropped substantially from whatever voltage you read before, it's definitely going to be an underground wiring problem, probably due to the water you mentioned.
4. IF the voltage in step 1 is 104V regardless of whether anything is connected or not, go to the main panel and read the voltage to the garage wires there.
5. IF it's 110V, then there's something drawing a lot of current underground.
6. IF it's 104, something else is going on and it's not underground, most likely. To be certain, just pull the wires from the main panel connection (panel OFF) and see if that brings it back to 110 or whatever. Make sure the whole house isn't seeing that low voltage.
Neglecting meter calibration, parallax error, etc., 104 V ac at the main panel and thus the whole house is right at the lower limit of usable grid voltage. In that case the problem most likely becomes that of the transformer out on the pole being bad or needing replacement. 104Vac is also tough on anything with a motor in it; they tend to run pretty hot. 110 to 120 V is the normally accepted norm, depending on where you live. Tolerance is allowed to be up to 10% but is seldom that far off for even the most remote areas.
If I've mistated anything I'm sure someone will catch it and correct it<g>.
HTH,
Twayne
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are off, just enough current flows to operate the sensors (which use only a couple watts). When something that uses more power, like the lights, are turned on, the high resistance can't provide the current and the voltage drops to near 0 and the sensors go out..
I assume he gets 104 volts when the sensor is on (lights switch is off).
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