My 91 accord has a charging system issue. The charging system light is on, and when I'm driving, the gauges are intermittent, the car begins to lose power, radio and accessories go out, and then car eventually dies while driving. I've replaced the battery and alternator, but there's still a problem. When engine is running, alternator output matches battery voltage (about 10-12v). I checked for continuity between alternator terminal and battery, and it's intermittent, depending on if the doors are open, ignition switch position, etc. When I start the engine, resistance is over 200 ohms from alternator to battery. What would cause this to jump from a dead short with the engine off, to over 200 ohms when the engine is on? Something is causing the connection between alternator and battery to be intermittent. I've also checked all fuses and they're fine. Could it be the Ignition Control Module? Or the ignition switch? Any suggestions would be appreciated.

It sounds like the voltage regulator is bad, brushes are worn down too far, or the rotor slip rings need cleaning. Regulated battery voltage should be 14 to 15 volts, not 10 to 12 volts. This link should help:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-10.html#post1973613

You likely installed a rebuilt alternator. Take it back to the store and ask for another one.

Disconnect the negative battery cable, pull back the rubber boot to the alternator's "B Terminal Nut," remove the nut, clean the connector with abrasive cloth, and apply dielectric grease. This is a prime source of resistance. Also, clean the ground going to the under hood fuse box and apply dielectric grease.

If you want, here's how to rebuild the alternator yourself:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-6.html#post666293