I have a 1976 300D that is not holding a charge on the battery. Things that keep this from being an easy (for me) fix: Battery is good and did well during load test; alternator is charging the battery; long drive with electrical going, battery dies next start; car started fine this morning (28 degrees F.) after sitting for two days; and finally, the problem started when I tried plugging in the block heater one morning and battery got drained (don't know if that was just a concidence or if that was the cause).

I have put the battery on a charger overnight and once longer, it takes a full charge, after driving around for a while, it was at 13.3 volts when I had it load tested. On a similar note, I am unable to locate the fuse box for the dang thing. I found four fuses on the firewall (three 16 Amp and one 8 amp), but think that there has to be more than that somewhere on the car. Any suggestions would be helpful. I am thinking that I should replace the wiring harness and the ground (ground is attached to a pretty rusted area of the body).