Hi Jeff;
Research shows that http://www.aircenterinc.com in Chattanooga markets its “Cool Air” system to many singles and twins. However the PA-31 is not on it’s website list as one it has converted. However, it claims it can install a Cool Air system in any 28 volt airplane. Contact Gary Gadberry at (423) 893-5444 to see if he can do your Navajo.
Just to be clear, I did not see the Cool Air system in the FAA Supplemental Type Certificate (STC) listing; however that STC listing is not always up to date.
One company that was listed is http://www.aircommcorp.com. In the STC files it’s listed as ACC-KP LLC in Addison, Texas. However, as I wrote above, the STC listings are not always up to date. It turns out that Air Comm Corp (in Colorado) purchased Meggitt, which had purchased Keith Air Conditioners.
For what it’s worth, I once installed a Keith A C system in a Cessna Skymaster. The compressor and fan are electrically-powered. Unfortunately, the current draw was very high; something like 50 amps as I remember. Since the two alternators on that Skymaster were 38 amp units, we had to upgrade the alternators to ensure that there would never be too great a draw on the airplane electrical system generating capacity.
Frankly, we were surprised that a STC was granted to an obviously flawed installation. And so was the owner when we explained the need for larger alternators.
In the end, the system worked well and I have to say it was a very comprehensive and well engineered installation kit.
