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Pertronixs & Erratic Tach

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MGretired

MGretired

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I recall a similar post on one of the BBS/forums, but I can’t find it in any achieve so I’ll ask the question again.
I run a Petronixs in the 69 B, had one for over 8 years with no problems. I recently had the distributor rebuilt by J Twist (as usual, a fantastic job!) and noticed the 8 year old Petronixs had a small cut in the wire, so I decided to replace it with a new one and use the old as a back-up. The car runs great with the new Dizzy, but I now have an erratic tach. I’ve heard that the Petronixs can affect the tach, although my old one didn’t. Any thoughts as how to fix the erratic tach?
 
On my 64 Austin Healey Smith's tach, the wire from the ignition to the coil passes through with a loop on the back of the tach. In order to get my tach to work, I had to make a double loop at the back of the tach (had to use smaller guage wire to get the second loop). Pertronix, however, recommended removing the existing loop and just allowing the ignition to coil wire to pass through the pick up at the back of the tach. Mine did not work that way, and someone with more knowledge than I suggested the double loop. So does my tach work??? Yes & No. Tach seems to work fine up to about 3800 rpm's, but then drops to zero. Frankly, I don't know if that is a tach problem or a Pertronix ignition problem. MoMa, an outfit who rebuild's LBC guages, says they have a fix, rather expensive, to make the tachs work with Pertronix, about $200.
 
MGretired, Just a suggestion initially. Put the old Pertronix module back in and see if the problem you are experiencing persists or goes away.Let us know how you get on. Page 16 referencd is not a solution for this problem---Keoke
 
Thats true Shorn, However, in this case," MGretired" and his car were at peace prior to: 1 rebuilding the Dizzy and 2 changing out the Pertronix module.---Keoke
 
Not a bad idea Jedi, I'll put the old petronixs in and see if the tach settles down. Won't get to it for awhile...I'll post when I do.
 
/ubbthreads/images/graemlins/thumbsup.gif---Keoke
 
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