Just get the whole lot done and replace with brand new is my suggestion.

Also a good reading with a multimeter won't always be accurate because the electric stress on the insulation at higher operating voltages will be greater and might not show when you apply only a few volts across it. You really need to do hi-potential testing of the leads to see if there is any leakage current. But that's probably taking it a bit too far

Anyone know what the operating voltage is?

PS: THumbs up for searching mastcell!!!