Simplified capacity control mechanisms for scroll compressors include a fork operable to open and close vents associated with a pair of scroll compression chambers. A single fork opens and closes both vents simultaneously. In the past, separate members have been utilized to open and close the two individual valves, and they have sometimes been actuated in a non-synchronous manner. A control associated With the fork is operable to move the fork between the open and closed positions by simple electronic controls. In several embodiments, the electronic controls are operated simply to stop and start the electric motor for driving the compressor. Pressure forces on and associated valve element move the fork to the desired position between the open and closed positions. No separate control wires, or separate electronic valves, need to pass into the scroll housing. In another embodiment, an electric solenoid is actuated to move the fork between open and closed positions.