Live Wire Detector problem

[george1981]

Hello,
I'm having some issues with my Bosch live wire detector as per the link at the bottom of the post.

It's a long story....

I'd like to drill some holes in a wall to mount a cupboard, the wall shouldn't have any live wires in it, however the previous owners had a habit of doing things to the house that they shouldn't so I tested for live wires.
Initially I swept the wall and it found nothing. After I'd marked where I was going to draw the holes I put the detector on them and it showed the lighting symbol for electricity but was the indicator was still green and wasn't beeping, I understand this to mean it's in the rough vicinity of a live wire but it's not a problem. Perplexed I checked again and this time the indicator went red and it started bleeping as if if was right on top of a live cable. I had someone else check and it went back to being green but showing the lightning symbol.
I then checked another wall where I know there is the cable for the light switch and it showed the symbol, went red and started beeping. I then tried it on another wall where I was sure there wasn't a cable and it showed the lightning symbol but stayed green and didn't alarm. I changed the battery and then tried again.
I went back to the original spot where I want to drill and now the lightning symbol may or may not appear, it stays green and it isn't alarming.
Any ideas what's going on? Or how I can check for certain that there are no live cables in the wall? I finished painting the wall yesterday so maybe the paint hasn't fully dried and is causing the problem?
The previous owners had a cupboard mounted on that wall and it was really high up, almost unuseably high which when the detector started going off made me suspect that they had to put it so high to avoid a live wire.
Any help would be greatly appreciated.
Cheers
George

http://www.homebase.co.uk/webapp/wc...ay?langId=110&storeId=10151&partNumber=277498

 

[securespark]

As you are hopefully putting a cupboard over the area, try gently with a small tool digging away at the area where the screw holes are to be drilled to see if there is a cable underneath.

 

[sparkiemike]

I have the "professional" version, and found the voltage detector would go off when I knew there no cables in the wall.

The only way I can use it is to switch off the power at the main switch and just scan for the copper cables & pipes etc

 

[plugwash]

The problem is that in order to sense a live wire at some distance from the surface those things have to be very sensitive. This makes them prone to false positives.

 

[canduit]

I used to have a Stanley device which claimed to detect live wires, etc, and I seem to remember each time you want to use it, it has to calibrated on an area of wall where it is known there is nothing lurking underneath. Defeats the object really, but at the same time it kind of makes sense.

 

[PrenticeBoyofDerry]

Hello,
I'm having some issues with my Bosch live wire detector

you will they are carp, not come across one yet that I would trust!
Follow securespark advice and isolate before you start poking around just in case you get unlucky!

 

[ericmark]

I have also found mine a little hit and miss. When you know there are cables and want to find out where not so bad but it seems to go off and not go off as you have said and I only use to help and don't rely on it.

However the CAT cable detectors I have used in the street are very good. I think just too many wires in the house.

Also of course taxi's, police, ambulance, fire, CB'ers, radio hams use a fair bit of RF and mobile phones, cordless phones, WiFi uses lower amount of RF and this can of course give false readings.

 

[EddieM]

I've never got any satisfactory results from them either despite having a "professional" model. however, one way i found of making it a bit more accurate, though I'd wouldn't say reliable, is the put ur free hand on the surface near to where ur doing the scanning. That said, i wouldn't trust them, mine would give a "live wire" positive placed on a wooden table!!

 

[EddieM]

I've never got any satisfactory results from them either despite having a "professional" model. however, one way i found of making it a bit more accurate, though I'd wouldn't say reliable, is the put ur free hand on the surface near to where ur doing the scanning. That said, i wouldn't trust them, mine would give a "live wire" positive placed on a wooden table!!

 

[george1981]

Thanks for the advice. I've tried the detector a few times yesterday and today and it's saying there's no live wire at all on both occasions. On saturday with the daylight I'll turn all the electrics off and see what it does, if it still shows no live wires I'll tentatively poke around by hand to see if there's anything there.
Thanks for all the replies
Cheers
George