Reefers And Temperature Control

If I have a refrigerated load, say at 43 degrees, will my reefer unit keep it from freezing if I’m traveling through an area with sub-freezing temps? In other words, does the reefer unit also supply heat when necessary to maintain a non freezing temperature?

Yep. It heats as well as cools, however, as far as I am aware, the temp for "keep from freezing" stops at like 68-70. I haven't messed with it to see what the upper limit is.

If I have a refrigerated load, say at 43 degrees, will my reefer unit keep it from freezing if I’m traveling through an area with sub-freezing temps? In other words, does the reefer unit also supply heat when necessary to maintain a non freezing temperature?

Nae Nae is correct. Pepsi and coke in many northern states use a slightly different reefer unit to keep their product from freezing.

Often times in the winter when we're hauling liquids (water, shelf stable juice, etc) reefer is set to 45 degrees just to prevent any freezing from happening. When our trailers get washed out in the winter they set them to 65 to prevent ice from building up, then adjust temp to 34 when they put it in a door.