Yes; Mike is right - it's time for a new one.
The Fluke 180 was (is) just a Bio-Tek 180 ... and I'm pretty sure I can recall using that one back in 1987 (OK, it may have been a 170).
may help to guide you.
one is good for reference purposes.
But "fluctuating voltages"? Have you taken a look inside? Have you got a decent earth?