Strange Circuit Test Reading

Ask your electrical related questions here
Post Reply
User avatar
A. Spruce
Posts: 5714
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Strange Circuit Test Reading

Post by A. Spruce » Sat Mar 09, 2019 10:57 pm

Hey guys,

I have one of those plug in circuit testers, the one with the three lights (red/amber/amber) that diagnoses circuit issues. A client was concerned that several outlets weren't grounded, when I plug in my tester it shows one bright amber and a dim amber light. If both lights were full bright, that is an indication of a correctly wired circuit. If only the bright light is on it is an open ground. So, it would seem that there is something between a correct circuit and an open ground. There are three known outlets on this circuit, they all read the same, one bright amber, one dim. Testing other circuits both amber lights are full brightness (correct circuit).

1 - What could cause this?
2 - Is this a concern for things like computers/electronics?
3 - Would installing a GFI at the start of the daisy chain or at all three locations be an acceptable correction of the issue, so long as all the GFIs are wired to line power?

The client bought a similar tester to mine, his tests were identical, one bright, one dim light on the circuit in question, both bright (circuit ok) on an unaffected circuit.

FWIW, I did a fair amount of dryrot work here last year, some T1-11 siding was replace in the vicinity of what I believe to be the lead outlet in the chain. While I don't believe I was anywhere near wiring, it's possible that maybe a wire was in the area where I was nailing. If I nicked a wire, do you think the culprit nail could be found with a multi-meter or wiggy?
If the women don't find you handsome, they should at least find you handy.

Jmaclicious
Posts: 247
Joined: Mon Oct 17, 2016 6:18 pm

Re: Strange Circuit Test Reading

Post by Jmaclicious » Sat Mar 09, 2019 11:11 pm

A. Spruce wrote:
Sat Mar 09, 2019 10:57 pm
Hey guys,

I have one of those plug in circuit testers, the one with the three lights (red/amber/amber) that diagnoses circuit issues. A client was concerned that several outlets weren't grounded, when I plug in my tester it shows one bright amber and a dim amber light. If both lights were full bright, that is an indication of a correctly wired circuit. If only the bright light is on it is an open ground. So, it would seem that there is something between a correct circuit and an open ground. There are three known outlets on this circuit, they all read the same, one bright amber, one dim. Testing other circuits both amber lights are full brightness (correct circuit).

1 - What could cause this?
2 - Is this a concern for things like computers/electronics?
3 - Would installing a GFI at the start of the daisy chain or at all three locations be an acceptable correction of the issue, so long as all the GFIs are wired to line power?

The client bought a similar tester to mine, his tests were identical, one bright, one dim light on the circuit in question, both bright (circuit ok) on an unaffected circuit.

FWIW, I did a fair amount of dryrot work here last year, some T1-11 siding was replace in the vicinity of what I believe to be the lead outlet in the chain. While I don't believe I was anywhere near wiring, it's possible that maybe a wire was in the area where I was nailing. If I nicked a wire, do you think the culprit nail could be found with a multi-meter or wiggy?
I actually had the same issue with my oven a while ago... thought my tester was broken but then i plugged it into my kitchen outlets and they were bright.. turns out the old wiring at the oven had a ground wire at the oven outlet but then at the other end in a junction box the ground wire was gone/broken.. and then new 8/3 wire was ran from panel to this junction and grounded to the box.. I just ran new wire from the junction to my oven and now it lights up correct.

User avatar
Aaron
Posts: 3197
Joined: Sat Jan 03, 2015 4:03 pm
Location: St. Paul, MN

Re: Strange Circuit Test Reading

Post by Aaron » Sun Mar 10, 2019 12:15 am

Yeah it sounds like an open or high-resistance ground to me. I would use a multimeter and check for 120V hot-to-ground. Take the cover off the first receptacle in the circuit and touch the leads to the actual terminal screws.

User avatar
A. Spruce
Posts: 5714
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Re: Strange Circuit Test Reading

Post by A. Spruce » Sun Mar 10, 2019 12:44 am

Aaron wrote:
Sun Mar 10, 2019 12:15 am
Yeah it sounds like an open or high-resistance ground to me. I would use a multimeter and check for 120V hot-to-ground. Take the cover off the first receptacle in the circuit and touch the leads to the actual terminal screws.
And the fix?
If the women don't find you handsome, they should at least find you handy.

User avatar
emtnut
Posts: 1789
Joined: Mon Mar 02, 2015 7:21 am
Location: Canada
Contact:

Re: Strange Circuit Test Reading

Post by emtnut » Sun Mar 10, 2019 7:11 am

A. Spruce wrote:
Sun Mar 10, 2019 12:44 am
Aaron wrote:
Sun Mar 10, 2019 12:15 am
Yeah it sounds like an open or high-resistance ground to me. I would use a multimeter and check for 120V hot-to-ground. Take the cover off the first receptacle in the circuit and touch the leads to the actual terminal screws.
And the fix?
First would be to turn off breaker, and find all the lights/receptacles on that circuit.

Then you give your 'best guess' as to how the wiring may be run. Try to find the light/recept that is feeding the 3 faulty outlets and test it. Keep going until you find the last good recept. More often than not, you will find the issue in one of the outlets.

If it is bad wiring, then isolate where the bad wiring is (by checcking the recepts, you should be able to do this). Then you can "ohm" out the cable. ie, twist the conductors together at one end, and check for 0 ohms at the other end.
~~ Ford Ford Ford Ford Ford Ford :mrgreen: ~~

User avatar
emtnut
Posts: 1789
Joined: Mon Mar 02, 2015 7:21 am
Location: Canada
Contact:

Re: Strange Circuit Test Reading

Post by emtnut » Sun Mar 10, 2019 7:12 am

A. Spruce wrote:
Sun Mar 10, 2019 12:44 am

And the fix?
Use shorter nails :mrgreen: :lol: :shock:
~~ Ford Ford Ford Ford Ford Ford :mrgreen: ~~

User avatar
A. Spruce
Posts: 5714
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Re: Strange Circuit Test Reading

Post by A. Spruce » Sun Mar 10, 2019 9:54 am

Ok, so remove the front door and install a new house! Got it! :lol:

I think I'll put the homeowner on the task of mapping the circuit. It's hard to say how the circuit is run, the panel is on the opposite back corner of the house and the outlets in question, two are on an exterior wall and one is on an unattached perpendicular living room wall.

Another question, circuit sniffers, are they any good? The homeowner bought this one and we had mixed results at best with it.
https://www.amazon.com/dp/B0014FNWJG/
If the women don't find you handsome, they should at least find you handy.

User avatar
Aaron
Posts: 3197
Joined: Sat Jan 03, 2015 4:03 pm
Location: St. Paul, MN

Re: Strange Circuit Test Reading

Post by Aaron » Sun Mar 10, 2019 11:43 am

A. Spruce wrote:
Sun Mar 10, 2019 9:54 am
Another question, circuit sniffers, are they any good? The homeowner bought this one and we had mixed results at best with it.
https://www.amazon.com/dp/B0014FNWJG/
No.

User avatar
emtnut
Posts: 1789
Joined: Mon Mar 02, 2015 7:21 am
Location: Canada
Contact:

Re: Strange Circuit Test Reading

Post by emtnut » Mon Mar 11, 2019 7:08 am

A. Spruce wrote:
Sun Mar 10, 2019 9:54 am
Ok, so remove the front door and install a new house! Got it! :lol:

I think I'll put the homeowner on the task of mapping the circuit. It's hard to say how the circuit is run, the panel is on the opposite back corner of the house and the outlets in question, two are on an exterior wall and one is on an unattached perpendicular living room wall.

Another question, circuit sniffers, are they any good? The homeowner bought this one and we had mixed results at best with it.
https://www.amazon.com/dp/B0014FNWJG/
It's always a bit of a guessing game, you have to think of where would the electrician run the wires from the panel to each device ... sometimes it makes sense, other times .... not so much !

I've only ever used a circuit sniffer in Commercial/Industrial. It can be critical if you shut of the wrong breaker. In a home, just have them turn of the TV and computer, and turn off breakers till you find the right one.
You need to spend at least $200 for a decent sniffer ;)

'Fox and Hound' can come in handy to trace out the wiring. They do take some getting used to, and best to turn off main breaker when using them (if not, you get ALOT of noise on the receiver)
~~ Ford Ford Ford Ford Ford Ford :mrgreen: ~~

User avatar
A. Spruce
Posts: 5714
Joined: Tue Aug 16, 2016 5:23 pm
Location: California, USA

Re: Strange Circuit Test Reading

Post by A. Spruce » Mon Mar 11, 2019 10:46 am

In thinking about how the wire was run, I suspect it is to the perpendicular, unattached living room wall, as it is closest to the panel. I checked the one at the kitchen that I initially thought was #1 and it seemed ok. I told the owner to map the circuit, so we should know more once that is done. I will probably also open the panel and have a look at the connections in there.

Thanks for the input on the sniffer, guys, I kind of figured that an inexpensive sniffer was probably too good to be true.

I will update when I have more info. 8-)
If the women don't find you handsome, they should at least find you handy.

Post Reply