Engine Mechanical problem
1997 Mercury Sable 6 cyl Two Wheel Drive Automatic 134000 miles
Put new alternator and new battery but alternator fails to charge battery. Tested alternator wires at alternator and all were good. Checked the output with a voltmeter at battery, numbers started at about 14.2 and continued lowering. Wondering if the ecm completes the charging system or if for any reason could be the problem.
The voltage regulator controls charging rate. It's bolted to the back of the alternator. If you look at it, you will see the four mounting bolts, and two more in between them. One might have a plastic cap on it. The other one is labeled " ground here to test. Let the engine idle, and ground that terminal. Watch the charging voltage at the battery and at the output wire. If they go up a bunch, say to 15 - 18 volts, the regulator is suspect.