I think there are 2 different issues here. The A/C shutting off and the Oil-Shuttle valve.
The Oil Shuttle Valve, where the oil filter is connected, routes oil to the oil cooler. The oil cooler is in front of the A/C, which is in front of the rad. There is no electrical connection to the shuttle valve, rather it is pressure regulated. Under normal oil pressure the oil goes through the oil cooler, but under idle, the shuttle valve does not allow the oil to go through the oil cooler.
This is the protection for the A/C--- Idle did not give enough air flow and the A/C gas pressure would get too high when it had the oil-cooler heated air coming through it. So the valve shuts off the hot oil to the cooler. When rpm and oil pressure rises, oil flow goes through the cooler again. (of course this was before the new design high volume fan came out and maybe the shuttle valve isn't needed if you have that fan.)
Since the ACR did not have a/c (except as an option) the shuttle valve was not necessary because there was no concern about high pressures in the a/c and oil could go to the oil cooler at idle.
As for the A/C cutting out under power, that is another item. Either electrical cutout or the vacuum drop shutting the airflow off.
