BCM not working? 88 REATTA

[Corbym]

I just got my first Reatta running for the first time since 2010, and it's got some expected electrical issues. The courtesy lights, dash lights, CRT screen (all except the radio function), and blower motor will intermittently work. The functions will seemingly work and shut off at random. I'm wondering what the best course of action in this situation is. Also, when the dash IS working the speedometer will not read any speed and stays at 0 while moving. The RPM display on the CRT works just fine however.

[2seater]

After long term inactivity and unknown storage conditions, the first thing I would check are the battery connections, ground and B+ connections inside the plastic boxes on the passengers fender and at the engine. Each of the battery cables consists of three terminals on the other end. Then move on to the ECM and BCM connections. Simply unplug and reconnect to get a new fresh connection, terminal spray cleaner optional. Lots of those items operate on lower than system voltage so connections are everything. Of course the wiring itself is subject to damage from vermin, but start with accessible connectors.

[Anthony]

All these things have in common the BCM connector. They also have in common ground G103, which is attached to the cylinder head below the generator (alternator).