Today I replaced the starter on our 99 SM to correct slow starting speed and a overcharging condition (16.2v). I replaced the starter with a new reman Denso unit. Once it was installed, the cranking speed was much higher. However, once the car was running, the battery voltage started at 17.2v and just continued to climb until I shut the car off at 19.0v. I reinstalled the the old starter and the battery voltage was steady at 15.8v.
Things I have checked or replaced over the past year.
1. New reman Mazda alternator (mid-season) to replace failed NAPA one
2. New cutoff switch (last year)
3. Tested system with alternate PCM
4. Tested system with alternate instrument cluster (charge light functions normally)
5. Checked continuity between alternator signal wires (Grey and Grey/Red) and PCM
6. Voltage drop checks between battery, cut off switch, alternator, starter, fuse box, and PCM. All less than 0.5v with car running
7. Ground locations for torque and general condition
8. Alternator belt tension
9. Battery (last year)
10, Battery terminals
11. Connectors at the starter, alternator, fuse block, and cut off switch
What am I missing? How can a starter cause the alternator just overcharge that quickly? Any thoughts on how to correct this?