The power-train control module (PCM) on certain years and models of the Mercury Sable controls the charging system by determining the best voltage (the optimal voltage set point) and sending the information to the voltage regulator. There are three pins on the voltage regulator. They're usually internal, within the alternator. One of these is the generator communication line, which communicates the set point from the PCM to the voltage regulator. The second pin is the generator monitor. This pin communicates load and error information from the alternator to the PCM. The third pin on the voltage regulator is the A-circuit pin, which senses battery voltage and sends this information to the PCM.
Remove the battery ground cable and secure it away from the battery's negative terminal. Jack up the right side of the Sable with the floor jack and support the Sable on the jack stand. Remove the right front wheel using the lug wrench. Remove the right fender splash shield using the appropriate sockets.
Loosen the tension on the accessory drive belt, using the appropriate socket to push the tensioner away from the belt. Lift the belt off the pulleys. Remove the crankshaft pulley using the appropriate socket. In most cases, you turn the pulley bolt to the right to tighten it and to the left to loosen it. The Sable's crankshaft pulley bolt is a left-handed bolt. Turn it clockwise (to the right) to loosen it.
Unplug the alternator's harness connectors. Unbolt the alternator mounting bolts and remove the alternator.
Install the new alternator, tightening the mounting bolts to 18 foot-pounds of torque. Reinstall the crankshaft pulley, keeping in mind that you must turn the bolt counterclockwise (to the left) to tighten it. Plug the harness connectors into the alternator. Tighten the crankshaft pulley bolt to 74 foot-pounds of torque.
Reinstall the accessory drive belt, following the routing diagram located on the fan shroud or the underside of the hood. Reinstall the right fender splash shield using the appropriate socket. Slide the wheel onto the studs. Tighten the lug nuts hand tight. Raise the Sable high enough to remove the jack stand, then lower the Sable to the ground. Tighten the lugs using the lug nut wrench. Reconnect the negative battery cable.
