Wet paper towels on the front door of standard nose locomotives would freeze and seal to some extent.
MRL experienced a serious runaway accident back in 1989 that is related to cab heat. NTSB doesn't provide electronic copies of reports that far back but below is a summary. As I recall (feel free to correct any errors) the MRL crew had some older power and the lead unit's auxiliary generator couldn't handle the extra load of the sidewall strip heaters. The cab was so cold the crew decided to switch out the consist on a grade to get a warm cab in the lead - may have been one of the through BN units. The crew bottled the air as they cut away to juggle the units and the train rolled backwards down hill. I recall the crew tried to chase it, even passing a red home signal, etc. etc.