I last had a car with autotemp about 15 years ago- a '69 LeBaron. The AC never worked. Is the consensus amongst the group that they are practically unfixable? Are owners essentially converting to "regular" AC? Or just doing without?
Well, I maintain that you can fix anything if you throw enough money at it.
Having said that, the early ATC, used on Slab Imperials and early Fuseys, is much harder to repair as there is absolutely no aftermarket parts support and the plastic pieces for all of the vacuum lines often are so cracked/ broken that it makes the system inoperable. Often hobbyists do not take the time to learn how the system works to fix it, or are discouraged by the cost.
The Autotemp II version with the under-hood servo (Fuselage cars)has aftermarket support because they were used on Mercedes cars. So you can often get them to work if you spend the money on the parts. The bonus is that the amplifiers that are made by the aftermarket are also a bolt on for the Autotemp II mark II version used on Formals (the servo was moved inside the car on Formals). The amplifier is the weakest part on the Mark II ATC, so it's good news.
Most Autotemp cars are sold with adds that say "AC needs charged" which like an inside joke for C body fans as we know that there is way more involved in getting these working.