Thanks Retiredcaps,
I purchased the tester new in the UK around 2003, but don''t recall exactly. I now live in Australia. I will have a look inside this weekend and may post again if I spot anything. As I said- I have never really used this function other than for novelty value when I first bought it so I am not too worried, unless it heralds further failures ! There is no voltage on the pins in the meter body, but I will check with a scope before I go any further.
I thought that the 30 ohms reading on the leads when the test button was pressed was a bit unusual- I had assumed that it would be a simple short.
Regards, BT