Battery won't charge on 86 760 Turbo, alternator checked OK

[volvodad]

Our 86 760 was not driven for 6 wet winter months. We dropped in a new battery this spring, it roared to life and was good for 2 days communte. The battery went dead. We recleaned the terminals on the battery and on the back of the alternator, recharged the battery and same thing, good for two days commute. Next, took alternator to parts store to bench test. All is well with alternator and regulator. Bought new belt and reinstalled alternator and recharged battery and good for 2 days. During this time, no idiot light lights, but amp gauge shows steady slow discharge. I scanned the engine compartment for burned, corroded wires. I did find some type of black relay switch about half the size of a cell phone on the right side of the engine bay by the firewall. Of the 4 or 5 wires leading into the "relay" about half of them had the inslulation rotted off so they were nearly bare. I rewrapped them, but still no charge to the battery. Any help or advice would be appreciated !!

[LaRy]

One possibility is that you have lost contact in the ground cable between the car body and the engine. It is thick and use to be blue. This could happen because corrosion, short sircuit or vibrations.