Our 16 seater bus has one of those heaters under the floor as well as three air con units. I have fitted a clock to the heater and it fires up 20 minutes before my scheduled runs. Really nice in the winter, nice toasty bus when all around are shivering
Can't do it with air con, it needs engine running and the electric power they use is rather high. You can hear the engine labour when you first switch them on due to alternator load.
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Ray at Wigan Pier
2014 A8L D4 4.0TFSI Gold (Sticker says "Beige") Can't leave you in a black smoke cloud anymore..
In progress, Nothing left to do.
Gone 2004 A8 D3 3.0 TDI. Ebony Pearl Black (with little bits of other colours and glitter)