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Fault Finding


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22 replies to this topic

#1 DeadlyDan007

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Posted 04 November 2009 - 10:47 AM

I am currently at college studying for my Level 3 tech certificate, have got level 2 already but am struggling with understanding fault findingBlushing
Does anyone have any hints or tips, or even websites that i could use????:D
Thanks Dan

#2 matt.leung

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Posted 04 November 2009 - 11:52 AM

just take the problem step by step and dont rush in....

#3 Robin Spark

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Posted 04 November 2009 - 02:20 PM

Its a bit of a crippler to get your head around this one at first, but fire away and ask whatever you dont understand cos there are plenty of good peeps on here who will help;)

#4 Guest_Dane_*

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Posted 04 November 2009 - 03:08 PM

Does anyone have any hints or tips, or even websites that i could use????:D
Thanks Dan


Ask any questions you have on here, even if it sounds very daft and you feel a bit shy to ask, DONT... Just ask, no question is a daft question!

some of the most experienced electricians may have to ask a question some day about an area there unsure about, and the person answering it may think its a daft question as the answers so easy as they cover that area of work daily.

It took me some time to actually get my head around it some times. But my advice

Always start with the basics, Make sure there is nothing plugged in (if on sockets) always start at the begging. (Il leave the word in so ya can all laugh! but meant to be beggining) :coat

Get as much info from the customer as possible! As a lot of faults start from plugging something in.

IE i had one recently ask why when i use my iron the power goes off...

If your searching for a tripping RCD without the above information, you could be there all day :)

All makes sense to me, but to others maybe not
Guiness Drink

#5 Evans Electric

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Posted 04 November 2009 - 04:01 PM

I have no idea what colleges want to know these days TBH but fault finding needs to follow a logical path. Same goes for industrial as for domestic. Go with what DL says above.
The biggest help is to listen to what people tell you , but beware of unrelated nonsense.
Things like :- Woman may casually mention that her husband fixed a kitchen cupboard over the weekend but has just noticed the kitchen plus don't work.
Or all power has gone , Well it was OK till I switched the cooker on and there was a big bang.

Never assume anything, such as an MCB is "ON" you still need to know that its passing current. Never assume the starter switch you have just shoved in a fluoro fitting is a good one, had three in a row duff 'uns straight from a new box of FSUs .

Testing is a logical progression really , rings can be a pain so divide ring into two legs , half of them work, so you have narrowed it down to 8 sockets , say, divide again and its between the board and the front room ,and so on.

#6 Theorysparky

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Posted 04 November 2009 - 04:02 PM

Ask any questions you have on here, even if it sounds very daft and you feel a bit shy to ask, DONT... Just ask, no question is a daft question!

some of the most experienced electricians may have to ask a question some day about an area there unsure about, and the person answering it may think its a daft question as the answers so easy as they cover that area of work daily.

It took me some time to actually get my head around it some times. But my advice

Always start with the basics, Make sure there is nothing plugged in (if on sockets) always start at the begging.

Get as much info from the customer as possible! As a lot of faults start from plugging something in.

IE i had one recently ask why when i use my iron the power goes off...

If your searching for a tripping RCD without the above information, you could be there all day :)

All makes sense to me, but to others maybe not
Guiness Drink


begging doesnt always help ;)

always ask questions on here if you are not sure
we all miss the obvious sometimes


and of course you may ask the question that someone else always wanted to know the answer but was scared to ask


always draw a diagram of the cct at fault and work in a logical manner

#7 Guest_Dane_*

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Posted 04 November 2009 - 04:09 PM

begging doesnt always help ;)


Maybe not always but when your in a fault finding situation there is always a place that is logical to start.

Me personally i always check everything is as it should be at the CU and start from there.

Again, it does depend on the circuit though. As above, rings can be a pain, but dividing them is the easiest way possible.

#8 sellers

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Posted 04 November 2009 - 04:55 PM

like said before. Never assume anything. Check it.

If you talking about a fault on a cable, Half it. find the half with the fault on, then half again. etc untill you find the link that is faulty.


Another peice of advice is have a clear head and a method of working. That way you know what you've done and what you haven't. I've seen people rushing round getting their heads in a right spin, with sockets off everywhere, cables out everywhere and no idea.

#9 Guest_Dane_*

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Posted 04 November 2009 - 05:15 PM

begging doesnt always help ;)


OH ****

I even replied not noticing my spelling mistake!!!

:coat:coat

#10 Theorysparky

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Posted 04 November 2009 - 05:21 PM

OH ****

I even replied not noticing my spelling mistake!!!

:coat:coat


i wasnt criticising your methods mate

just a funny spelling mistake :P

#11 Guest_Dane_*

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Posted 04 November 2009 - 05:25 PM

i wasnt criticising your methods mate

just a funny spelling mistake :P


i know hehe, just cant believe i didnt notice it even when you put it in bold lol

#12 green-hornet

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Posted 04 November 2009 - 07:23 PM

I would agree with all of the above.
I always start by asking questions, this could indicate where to look first, but remember they are sometimes very vague with the answers, until after you find the fault.
If the fault is on the ring circuit I make sure everything is unplugged, then I do the normal tests at the cu you would do to verify a circuit. End to end r1+r2 insulation etc etc. If you use some connectors you can test out at each socket, and depending on the fault get an indication on your tester with the results you get.
It is a good idea to narrow down the ring, split in half which has been mentioned, and doing a wander lead method check continuity, this can be the fastest way of finding a split cable or loose connection.
If the fault is nuisance tripping of RCD check what the customer was doing last time it tripped, there may be some clues given as to why.
On lighting circuits I always link out at the cu and do a continuity check, most causes of faults are the diy new light fitting and switch wire put with the rest of the nuetrals, loose nuetrals, and heat damage to cables.
It can be trial and error especially when you get intermittant type of faults, I had one last year where a nail had gone through a cable, the nail was removed but the hole and damage was not repaired.
On testing the insulation was ok lower than 200 but ok, and whilst there everything looked ok, until they closed the kitchen door!!?
I found out that when the door was closed it put extra pressure on the hidden cable, effectivly opening the "wound" and causing the arcing that set off the trip.
It had been left like that according to the landlord for 7 years, and had only now become a problem.
So you see sometimes we all have to scratch our heads.

#13 Evans Electric

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Posted 04 November 2009 - 09:15 PM

like said before. Never assume anything. Check it.

If you talking about a fault on a cable, Half it. find the half with the fault on, then half again. etc untill you find the link that is faulty.


Another peice of advice is have a clear head and a method of working. That way you know what you've done and what you haven't. I've seen people rushing round getting their heads in a right spin, with sockets off everywhere, cables out everywhere and no idea.


Good point this. I've seen it happen a lot . The Scalded Chicken Syndrome.
Always a case of " Don't panic Mr Mainwaring"

A sparks I know asked me to meet him at a job, he was having problems.
A large house divided into flats with a common stairs, lights don't work.
He'd brought with him a replacement, fuseboard mounted, delay lighting relay. Push switch on each landing. He said he'd changed it once but lights still do'nt work. Quite expensive MK ones.
While he opens the board I opened a light fitting, those round B&W plastic pill box shaped ones, lamp is blown.
Check them all , four have blown lamps, two have been nicked by residents.

The sparks had convinced himself that it must be the timer, ended up with two on his hands.

#14 DeadlyDan007

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Posted 05 November 2009 - 03:41 PM

thanks for the help, I will definately keep your ideas in mind, and will probably be asking alot more questions in the future!

#15 binky

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Posted 05 November 2009 - 08:35 PM

Did some fault finding yesterday - couldn't understand why 2 way switching via an intermediate wasn't working properly - re-wire switches a dozen times, still couldn't get to work, eventaully took to checking continuity of cables - broken conductor on Brown, and grey cable one end connects to brown on the other - no wonder I couldn't get it to work properly - moral is ask the customer more questions in the first place, it saves a lot of irritation.

Fault finding today on property I've been to before - part of downstairs lights not working - inspect accessories - poorly wired pendant. Gave a shake, lights come on/ go off. Diagnosis loose neutral terminal in pendant. Fault finding should always be logical but a good visual for obvious faults can save a lot of time.

#16 revjames

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Posted 05 November 2009 - 08:55 PM

I have worked as a maintenance spark on many occasions in factories etc as well as the domestic side so have had a lot of experience with fault finding. I would say the best advice is look for the obvious simple things first. It is unlikely to be anything complex and more likely to be something stupid. I recently attended 2 faults in a new property. 1 was a screw through a lighting feed (the guy who fitted the ceiling was to blame for that) and a badly fitted hallway switch which was allowing a terminal to touch the mounting box screw lug.

Always check the basics!

#17 Guest_Dane_*

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Posted 05 November 2009 - 09:00 PM

I have worked as a maintenance spark on many occasions in factories etc as well as the domestic side so have had a lot of experience with fault finding. I would say the best advice is look for the obvious simple things first. It is unlikely to be anything complex and more likely to be something stupid.


Like a contactor not working... whack it wi big end of screw driver lol incase its sticky :D

#18 Theorysparky

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Posted 06 November 2009 - 08:35 AM

[quote name='binky']Did some fault finding yesterday - couldn't understand why 2 way switching via an intermediate wasn't working properly - re-wire switches a dozen times, still couldn't get to work, eventaully took to checking continuity of cables - broken conductor on Brown, and grey cable one end connects to brown on the other - no wonder I couldn't get it to work properly - moral is ask the customer more questions in the first place, it saves a lot of irritation.

had one of those faults a few weeks back

turned out to be a faulty low energy light pendant Blushing

#19 jabzuki

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Posted 06 November 2009 - 05:39 PM

...as people keep saying, "never assume"!
I got called to a light fitting the other week with an intermittent fault. Customer advised me that he'd replaced the bayonet fitting, so I just checked all the switches (terminations, operation, etc) and all seemed fine. Only to get called back the next week.
It turned out one of the pins in the lampholder was sticking and arcing.
A basic fault that ended up taking two visits... so never skip the basics!

#20 Robin Spark

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Posted 06 November 2009 - 08:42 PM

Might be coincidental but I have recently had 2 ring ccts with end to end continuity open cct so in effect creating 2 radials. On both occassions it has been in the kitchen where the sockets have been spurred off and conductors have not been terminated properly in the back of the socket.




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