Plug-in heater:

Need some insight on cigarette plug-in auto heater. Has anybody used one & are they worth buying?

Thanks in advance,
jackspita

A heater big enough to heat a truck cab needs to be wired directly to the battery. Probably at least a 30amp fuse.
Do you want a little warm air for the windshield or a bigger unit than this.
I would recommend fixing the car heater you will be much more happy.