...I think we're jumping around from the original thread but...
I have a FRESH air heater and it does not have the tall slender door. FRESH means just that, a heater that draws fresh air from the outside cab vents. Then the recirculating heater and the "plain" heaters.
We've beat this heater thing to death and somewhere, there is a thread with each of them and description. I just haven't found it yet. Then there is always the question of what year had what and when it was available. Gosh, I love it. Keeps my mind active and from becoming, uh, whats the word for forgetful? Dementia, that's it.
