I just bought a brand new battry for my 77 300D and it wont hold a charge what might be the problem?
There are many problems that could cause a new battery to lose it’s charge. Start with the obvious…have the alternator checked. If it’s okay then move on to slipping belts, loose connections and bad wiring/electrical shorts. Also, check your battery light. Just turn the key on and the battery light should come on with the rest of your dash icons. You need the light in order to energize the alternator so it can charge the battery.
I’m not clear on what you’re saying here. Is the battery drained only after it sits for a while, like a few days? Or does it not charge up as the car is running in the first place?