Hi Erick,
I think you mean the warm up device shuts off the air supply when warm not cold.
You have the 1971 version of the emission control system. There is a low coolant temperature switch located in the block on the fuel injector pump side of the engine. When the engine is below 62 degrees F the switch should be closed. When this switch is closed vacumm pressure is released, by the two way valve, on the distributor and timing retard is removed. This creates quite a rpm pickup when the engine is cold. You can simulate this action by jumpering the low coolant switch wire to ground. My switch is broken in the open mode as I suspect many others are.
Jeff C.
1970 280SL 4-speed