Re: 1939 Paxkard Six- Convertible coupe headlight bucket

Posted by HH56 On 2019/6/5 11:10:03

I think the biggest issue with the 6v Pertronix is voltage drop when the starter is cranking or bad connections or the generator isn't genning properly and not putting out the typical 7v charging voltage which results in a low voltage to the Pertronix unit.

Most of the solid state logic typically used in items like the Pertronix use what is called TTL logic. That requires 5v to operate properly and is very fussy when the voltage moves in either direction just a tiny fraction away from 5v. The voltage is supposed to be regulated at 5v in the Pertronix but the regulators need headroom to do their jobs. When running at 12v there can be a huge amount of voltage drop and the TTL logic will never see it because the regulator can do its job so the ignition works very well. When running at 6v, if the starter pulls too much current or a bad connection has dropped the voltage available to the TTL regulator down to below 5v or even to a point above 5v but where the regulator cannot function reliably then the TTL logic also sees the voltage fall and either does not work at all or becomes very erratic.

Most of the people that reported Pertronix issues seems to have had issues with unreliable starts. That would indicate the starter motor is pulling a lot of current and the battery or cables can barely supply the starter let alone supply an adequate voltage to the Pertronix so it starts to misfire or not put out a spark.