Howie wrote:
My MIL has just moved house and it has a number of outside
lights. Some are 12v and some are 240v.
A couple of circuits aren't working and the cables are buried
underground. Does anyone know of a way of finding the route
and/or checking where a cable break might be, - without digging
up the entire lawn! ??

1. Find yourself someone who does groundworks / pavement repairs and has
a C.A.T. (Cable Avoiding Tool) - a cable detector on steroids - and ask
him to wander over your lawn. You can hire them from about £6 a day[1].
That will get you the cable route.

2. Get a capacitance meter and measure the capacitance across each end
of the cable. The ratio of the two figures will show about how far along
the cable the break is. That will get you where to start digging.

3. Ask previous owners where they buried the figging stuff.

Owain

[1] Hire (7 day minimum)
http://isswww.co.uk/Test%20Equipment...ault%20Locator

[2] Hire
http://www.surveyexpress.co.uk/C-ScopeCat.htm