Welcome to the Fourms and the world of Vintage Airstream ownership!
Originally Posted by BurnBound
I'm a total newcomer to my renovation project and was hoping that someone could tell me what kind of airconditioner I would need for a 1972 Ambassador or a good refernce to help me figure out what kind I would need.
The one limiting factor in the selection of an air conditioner for an Airstream is the availability of a condesate drain pan (these are available only through Airstream delaers or authorized repair centers). These condesate drain pans are only available for select makes and models of air conditioners and a check with an Airstream dealer or service center will reveal the current selection(s) available. A condesate drain pan is an accessory device that installs below the air conditioning unit to collect the condesate and direct it through the condesate drain tubes that are routed through the wall cavity at the factory. If you don't mind having the condesate drain on the roof and down the sides of your coach, then any of the modern RV rooftop air conditioners is a possibility.
If your coach has never had a roof air conditioner, you need to be prepared for something beyond a typical installation. Airstream didn't use an existing vent opening for its air conditioners - - the air conditioner was "cut" into the roof a specified distance from the front main bow (junction of front dome and main roof panel) to the rear (this distance can be found by consulting a factory service manual, contacting your Airstream dealer, or Airstream Customer Support). The coach should be pre-wired with the wiring coiled so that it is available at the factory specified location, and the condesate drain tubes should also be found in that location as well.
If your coach has an original Armstrong Bay Breeze, the removal may be a little more involved than expected as it is a two piece unit with interior and exterior components joined by some "plumbing". Removal may be time consuming to find and disconnect all of the attaching hardware.
Both of my coaches have undergone air conditioner replacement (Overlander) or new air conditioner installs (Minuet) using Coleman air conditioners - - the Overlander has a Mach series 13,000 btu while the Minuet has a Mini-Mach 11,000 btu unit. The lack of condesate drain pans for these air conditioners has bee a bit of a learning experience - - I thought that I would be less satisfied with the resulting installation on the Airstream (where it actually has been very satisfactory) and expected to be very well satisfied with the resulting installation on the Minuet (where it actually has been less than satisfactory as the condesate has caused rust streaking on the sides of the coach).
Good luck with your investigations and the project!