Pertronix Positive Ground Question

[fwtexasbj8]

I just installed a Pertronix positie ground system in my 65 BJ8. Everything is working and I am seeing the same tach inconsistencies noted in numerous posts on Pertronix conversions.

The one anomoly I cannot figure out is when I had the white/black battery ground wire disconnected like the Pertronix instructions said, I noticed my voltmeter was reading like the charging system was not charging the battery (only reading ~12 volts). I read several posts regarding reconnecting the battery ground and decided to hook it up again. Much to my surprise, my voltmeter began reading a normal charging voltage. My voltmeter is wired like I read on this forum to the fuze block. I cannot figure out how the battery wire could affect the charging system reading.

Does this sound plausible? Has anyone seen this issue with a Pertronix system?

Thanks for any help.

Doug

 

[GregW]

Hi Doug,
When you were checking the voltage, where was the other lead attached?

 

[fwtexasbj8]

I have the second lead out of the voltmeter grounded on the speedo bracket. I think this is the same ground all the dash lights use but when I measured continuity to the chasis, it was strong.

 

[vette]

Doug, when you had the white/black wire hooked up and were reading better voltage, did you take notice to how the tach was reacting. Was it better?

 

[GregW]

I’ve been scratching my head on this one. The only thing that makes sense to me is the voltage regulator was cutting in and out between the time of the two readings.

 

[Dave Russell]

This is all very confusing.

Is your pert. connected exactly as on the attached drawing?

Can you describe exactly where your VM is connected?
D

 

[vette]

Greg, I was thinking along the same lines. Maybe when he first checked the voltage the battery was full up and not taking much charge. Then later after multiple starts and short runs, it needed the charge.
That's why i was curious as to whether the tach showed any difference. I don't think the white/black wire could have had any ground while running or it would not have run. But I wonder if having the white/black wire connected could change the total Impedance of the circuit that the tach and pertonics would be reacting to it. I really don't think so...but?

 

[vette]

By the way, Good drawing Dave. I have a question about it though. Would the coil have the negitive side connected to the switch on a BJ8. I'm thinking the BJ8 already had the electrical connected with negative ground then the coil would have negative on the breaker side. I always get this mixed up.

 

[Dave Russell]

To my knowledge ALL Big Healeys had positive ground. So negative comes from the switch.

A battery that was full charged & still being lightly charged, would have at least 13.5 volts on it.

I don't know where the VM is actually connected though.
D

 

[fwtexasbj8]

Dave,
Sorry it has taken me so long to reply but I was out of town this week.

I double checked today and verified I have installed the ignition exactly like your diagram as best I can tell. The white wire I spliced into the black Pertronix wire is the one that connected to the - post on the coil.

My VM is connected to a spare terminal on the top 35 amp fuze block at point 4 on your diagram. This is the switched side and as I read about on this forum, gives me a dual indication of charge and condition of the fuze.

Vette, the only difference in my tach operation is it now runs a little fast when compared to the tach measurement on my dwell meter. It seems consistent and strong, just a couple of hundred RPM higher with the Pert than before.

Thanks for all your help,
Doug