Even BR staff used to get confused about which locos could provide ETH/ AC. (ETS these days).
Riding behind 40150 on Mk2 air cons from Preston-Blackpool North on a hot day, the bashing fraternity wedged all internal doors open and ensured all droplights were open to get a flow of air, as the 40 couldn't provide AC. The guard came round closing them again until it was pointed out quite forcibly that we would cook. He wasn't aware that the loco couldn't provide AC.
A few weeks later, on a Salop-Whitby excursion, behind a 47/4, it was distinctly cool, and on arrival at Sheffield, a loco change ensued. The guard confidently told us that we'd warm up now...No chance, a 47/3 was provided, which never had any form of train heating.
There were doubtless 1000s of similar instances up and down the network over the years.