Graeme, are yu talking about the effective resistance under load? If so, simply changing a lightbulb from 60W incandescant to a compact fluorescent would change the reading.

If we are talking about something like the insulation resistance, that reading can be significantly affected by atmospheric conditions, particularly humidity.

The only solutions really are in detailed documentation, number of points of all types, details of the circuit breakers, and photographs - lots of photographs. I think murdock's idea of printing out the critical readings taken and making that part of your filed documentation is also pretty sharp.

The real challenge here is that when an "accusation" is made, the basis of attack is that the problem "must have been there" at the time of the issue of the COC. And all the pressure is on the issuer to prove, not only that the problem wasn't there at the time he issued the COC, but also how the situation changed.

In terms of SA law (innocent until proven guilty), it is up to the accuser to prove that the problem existed at the time the COC was issued. It simply isn't good enough that this proof is "becuase it is like this now, it was definitely like this then." Further, folks who say "nothing has been done since" when in fact they know that something has been done are guilty of fraud!

But things simply aren't happening that way.