Have the battery load tested, if good then check both battery cables for corrosion under the insulation. As HRL pointed out, check the negative cable at the point where it connects to the frame, engine, firewall.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
| 
