Me wrote:

"wintertime heating" ?????? Come on give us all a break. Why in the
world would a Design Engineer spec an Low Vlotage Electric Heating Unit
for a Bus, when they are throughing away, Orders of Magnitude, more
energy out the cooling system, of the engine that is powering the Bus?
This is beyond Stupid, and very near Moooorrrroooooonic.........

They wouldn't; however, pumps and fans add up.

SFWIW, there are at least a couple of manufacturers who provide stand
alone oil fired heating systems for trucks and buses.

You can take your meds and go back to sleep now.

Lew