Yes I know we're only into February, and there's most of the year still to go but I've a feeling I'm in the running for this years title.
As I had an issue with my alternator overcharging, I swapped the regulator off my Elite alternator with the one on my CD. This moved the point where the overcharging would start but didn't cure it.
As an alternator swap is not a two minute job on a 2.5td, I took the Elite's alternator to be bench tested first.
Turns out that it was totally dead. Not a glimmer of anything at all. Strange, even a faulty alternator would give something. Over or under charging etc. It was working fine when the car was in use.
Oh well, c'est la vie, so I bought a replacement alternator, fitted it and the charging issue was sorted. Happy days, I thought.
This afternoon I gave the two "faulty" alternators a clean down before returning one as the exchange unit to save £50. I took the covers off to swap the regulators back and found the Elite alternator that had been confirmed as totally dead had no regulator fitted.

I fitted the regulator and sheepishly went back to have it bench tested again.
The out-come ? It was fine. A1, spot-on, no problem...AAAGH !!
£100+ spent for no reason...other than being a total numpty

Top Tip: Engage brain before allowing hands holding tools near vehicle....and especially before reaching for ones debit card.