[66tbird]

On There Web Site Pertronix.com Under Faq You Will Read, About Low Voltage Thats Where You Have A Res. Wire Or Ballast. If You Check Voltage At (+)pos. Side Of Coil While Engine Is Running. If Voltage Is 4.5 T0 About 7-8 Then You Have A Res. Wire Or Ballast. If You Do Your Car May Run Rough. It Gives You A Test. (jumper To Battery). I Will Say When Changing To Another Power Supply For Your 12 Volts. Make Sure It Remains At 12 Volt When Car Is Running,it Is Keyed Only In Run Position,not Assy. Side Of Key.some Say They Run Fine Without Change Mine Needed Changed. Hope This Helps