I am not an expert in all the electircal things involved with the voltage regulation system. However I know that when the retgulator senses a need to charge the battery more, it allows the voltage to rise.

My own experience with this was in a 1975 245DL, some years ago. I had skimped on a battery hold-down, allowing it's weight to hold it in place. Big mistake.

We drove at light on some 20+ miles of rocky road, lights on all the way. Then we stopped to do other things for an hour or so. Then drove a few miles to the motel where we were staying.

Next morning it was dead as a doornail, not even a click. No lights, nada. Got a jump start, and it ran. Heard a loud rapid clicking inside the cluster, and the lights were very bright, but continued on to a service station. Checked the battery, it had 2 dead cells.

What had happened? The rocky road jouncing loosened up the lead oxide on the battery plates, and it fell to the bottom of the cell, creating a dead short.

The battery was unable to receive a charge, so the voltage regulator kept raising the voltage. The clicking was the 1975-style voltage regulator in the dash attempting to get the voltage down to the 5 volts needed for the gauges.

So why this story? You have a problem somewhere in the alternator-to-battery-to-alternator loop. It is impeding the battery from getting what the voltage regulator sees as a full charge, so it keeps raising the voltage.

Check the ground wire from the alternator to the block. Check the ground cable from the firewall to the engine (there's one like that on a 240).

Check both battery cables for corrosion up inside the insulation. Check the cable connections of the red cable from the alternator to the starter, and from the starter to the battery. Check the ground connection from the battery, too.

Post back with how that works.

Good Luck,

Bob

:>)