How to adjust very old Yale door closer

[ColinP]

Looking for anyone who is familiar with or has worked on one of these. The Ironmongery I believe is original from the building and is quite old.

The closer itself is functioning however with too much force and is causing the door to bang very loudly on every use. I would like to reduce the tension on the closer so that it no longer bangs and doesn't damage the door/frame. Ideally without replacing the closer.

Any guidance on how to adjust the tension/special tool requirements or even identification of the model so I can look for an instruction manual would be gratefully received.

Images below:

Thanks in advance

 

[AC Power]

That door closer operates on the same method as does a garage's overhead door. The overhead door is opened and closed with the assistance of a spring that is axially wound with a tremendous amount of energy, as a small residential overhead door can even weigh 300-500lbs (130-230kg).

While I don't know how to adjust (reduce tension) on this device, I am telling you for safety reasons....be careful! Don't loosen that flat screw pictured in your 3rd and 4rth picture. As is the case with overhead doors, you might release the entire tension of that spring one fell swoop, and get lacerations to your face and hand. I would ask an overhead door mechanic, maybe he'll know (perhaps by examining and device on-site) how to relieve the retaining screw by manually countering the wound energy with pry bars or open end wrenches, then he could back-it-off a few rotations to reduce the closure speed/force.