I went to start my 70 Charger today and at first I thought I had a dead battery since it clicked a little and the dome light was dim. I put the battery charger on it and it looked like the battery wasn't taking much of a charge. I had driven the car a few days ago and it was fine. I checked the voltage at the battery with my multimeter and it is 12.5 volts (with no load). I jumped the starter relay and I got a spark and the stater solenoid clicked a little. I tried turning the key again and got a buzzing from the starer relay then I tried it again and I get nothing. The starter relay won't even click. The dome light still comes on very dim but voltage at the battery is 12.5. I checked voltage across the starter relay and it is 12.5 there too so it should not be a battery connection issue.

How can I have 12.5 volts at the battery and across the starter relay but my dome light be very dim????