(07 Dec 2022, 7:47 am)mb134 wrote Bar a small handful of vehicle types (Optare Solo's spring to mind), I don't think drivers have any control over passenger saloon heating.
In terms of MMCs, I find it interesting that your experiences on them are constantly cold. I commute to work on a route that primarily uses E400 MMCs and, bar one or two, they're always warm - most days I need to take my coat off. They're never as obnoxiously warm as some older deckers, but I don't believe they're meant to be, I'm sure the heating is controlled by a thermostat so it'll turn off before it starts to boil everyone onboard.
Note on the vents at the front, unless the bus is fitted with an air conditioning unit, the air coming through won't be air conditioned.
What's the classic E400 bodies like in winter at Arriva Northumbria? I only ask as the 15 plate examples at Darlington seem to get colder every winter especially on the top deck, dread having to use them at this time of year and have complained about this to Arriva previously but nothing was done (last year one example was made worse by blocks being installed on all bar one of the top deck windows as a COVID measure, could really feel the cold on windy/icy days).