@MJF — can you share more about what you did with your H53 ATC? I’m going to be redoing it on Ming (my ‘73 NYB).
PS:
@saforwardlook has experience with this replacement servo.
I have replaced the original servo in my 1972 Imperial about 10 years ago now for two reasons. Besides the factory unit leaking due to its bakelite (kind of a plastic material) body and hose base outlet/inlet due to cracks (just like the non-autotemp factory heater control units made of the same material) which happens in about 2 years of normal driving, it was no longer operative. So I bought the system from Performance Analysis Company:
ACC Version I
These reproductions are possible only because Mercedes Benz bought the patent rights to use those units on their Mercedes Benz models, but with upgraded materials in the form of aluminum for the main body and base outlets, thus fixing the design deficiencies of the original Autotemp II factory units. The factory units were used up shortly after the systems had run their course since every car using one needed a new servo in just about 2 years due to the bakelite material usage. Thus no nos units were available a few years after production.
But Performance Analysis company rebuilds these units with new housings of aluminum and upgraded components and electronics and the one on my Imperial, not driven regularly though, but fairly frequently compared to my other cars because it is not a show queen but just a really nice vehicle. It still works and modulates fine after all this time. I also bought a new amplifier at the time too.
I will never go to the new one available as highlighted above by MJR (I think he is the one that bought his T&C wagon from me a number of years ago and has done great things with it) only because original in every aspect as much as possible is important to me for my cars, but if original appearance is not a big factor, then the new option above might be just fine. I am not sure where the hoses hook up, etc. since no such provision is shown, but it likely won't look original.
When I bought my Performance Analysis Company unit many years ago, the price was about $800, but that included the amplifier too, so their prices have not changed much over the years.
