12v key on problem

You need to make certain that IGN1 and IGN2 are interconnected (easiest) at the old ballast connections. The IGN1 usually dark blue GOES DEAD during crank. IGN2 is the resistor bypass circuit, usually brown. Both these come from the ignition switch. IGN2 is the only source of ignition during cranking and must be interconnected

If the voltage is still low, and the battery is above 11-11.5V when cranking, check "the path"

Starter relay--fuse link--through bulkhead connector--to ammeter circuit--to ignition switch--back out of switch and connector--back through bulkhead---to ballast connections and to coil

Low voltage/ poor connections/ voltage drop in this circuit will ALSO case over charging

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