Nice and warm air, no antifreeze smell, I have had a heater core go bad on me before. I was just curious if this was normal or if i had a problem. the guy I bought the machine from had bent the frame and popped the window out. I straightened it and put the window back in it, but the machine was run for a few years without it. I am gonna pull out the vents and clean the crap out of them. We'll see how that helps.scrapecc: Is the heater blowing warm air? If it is blowing warm air good the next thing I would say to look for or smell when in the cab that smells like antifreeze if so you will need a heater core. If blowing warm air and no antifreeze smell you might need to get your vent and def. replaced. Also you said there are broken vents you may want to do the mouse nest check going into the fall t.p. is a good duct plugger. One other thing is are your boots or pants cuffs wet or full of snow? Case 580 Super M fogs up bad with wet boots and pants or coveralls to much humidity!
I'd keep a window cracked too. All the humidity has got to go somewhere. Does your machine has AC too? If so, run it. It will dry out the air.