The dual fuel/vaccum pump is AC model BK/BN and was around since the 40's and my manual lists 2 different part numbers for them in total.
The easiest way to ID an AC pump is by the model number stamped on the mounting flange.
Most AC pumps give the same pressure/volume per stroke so really they are mostly interchangeable. As to what is right the Master Parts List may help. I have at least 6 AC pumps to choose from (singe, dual, glass pulsator dome or metal... they all seem to have worked on the 235s that I have.
Last edited by pfarber; 11/24/2013 5:58 AM.
