I have a question, I dont want to destroy the tach on my gt500, what do I have to do when wiring the Pertronix 3? Thanks for the help.
I wired mine up per the Pertronix supplied instruction sheet. Tach works fine. Others may have differing opinions.
The II and III will not work as per Pertronix.
After my conversion, my tach seems to be reading about 200-300 rpm low.....
The Pertronix device should not cause that if it is wired properly. One other thing can cause the tach to read low or high is using a coil with incorrect resistance. The tach detects current to give accurate RPM. If the coil is lower or higher resistance than stock then the tachometer cannot detect the proper current.
Quote from: oldcanuck on April 20, 2020, 09:13:11 AM
After my conversion, my tach seems to be reading about 200-300 rpm low.....
I wired per the instructions, but I replaced the old non-original coil with a new Pertronix Flame Thrower coil as I thought that is what was required for the HEI ?
Is that were I goofed....... ?
Yes indeed. The Pertronics coil is lower resistance than the stock coil. So it gives a higher output to the plugs but ruins the performance of the tachometer.
Personally I prefer using the stock yellow top coils.
Quote from: oldcanuck on April 20, 2020, 09:47:03 AM
I wired per the instructions, but I replaced the old non-original coil with a new Pertronix Flame Thrower coil as I thought that is what was required for the HEI ?
Is that were I goofed....... ?
Despite the information given here, the Pertronix II and III will not function as wired by ford with the tach. Not an assuption, but fact. It MUST have a 12V power source to the module. Even the Pertronx I require it, despite them running... For a while. I have a Shelby with a factory tach and have been through this.
The diagram Pertronix supplies is NOT Mustang specific and is wrong. It's why I keep talking to people in messages and giving them instructions to walk them through. The II and III will damage a factory tach without proper wiring.
Many wind up getting talked into a three-wire tach movement when they don't need it because of this.
I completely reject your opinion.
Quote from: The Going Thing on April 20, 2020, 02:16:53 PM
Despite the information given here, the Pertronix II and III will not function as wired by ford with the tach. Not an assuption, but fact. It MUST have a 12V power source to the module. Even the Pertronx I require it, despite them running... For a while. I have a Shelby with a factory tach and have been through this.
The diagram Pertronix supplies is NOT Mustang specific and is wrong. It's why I keep talking to people in messages and giving them instructions to walk them through. The II and III will damage a factory tach without proper wiring.
Many wind up getting talked into a three-wire tach movement when they don't need it because of this.
I really could care less what your opinion is. You're wrong and I have an original tach car and at least seven people here who corrected their issue with my help.
It's not a guess, it's an issue that even Pertronix was given information to correct their generic tach wiring instructions which don't work. Phil Severance also recommends the same method I use. If you wire a Pertronix II direct they are several hundred RPM off.
Your BS and know it all attitude is why I stopped posting the information openly. I'm sorry your ego is bruised.
I've been installing and using Pertronix devices since the early 1990's and have never had one fail or anything happen to a factory tachometer as a result. You are simply either unable to read schematics properly or you don't have good information at your disposal.
Here is a simplified schematic of how to properly wire an original Pertronix or the Pertronix II in our cars.
Quote from: The Going Thing on April 20, 2020, 02:47:38 PM
I really could care less what your opinion is. You're wrong and I have an original tach car and at least seven people here who corrected their issue with my help.
It's not a guess, it's an issue that even Pertronix was given information to correct their generic tach wiring instructions which don't work. Phil Severance also recommends the same method I use. If you wire a Pertronix II direct they are several hundred RPM off.
Your BS and know it all attitude is why I stopped posting the information openly. I'm sorry your ego is bruised.
There's a much easier way to do it. That is the crap that Pertronix hands out. I'll just keep helping people fix the issue at hand.
Actually the drawing was done by a friend of mine because the Pertronics information is so hard to follow. Again you are making generalizations that are incorrect.
When the drawing was made he placed the word Resistor on both wires coming to and going from the coil. The one on the left should not be there.
Quote from: The Going Thing on April 20, 2020, 03:07:53 PM
There's a much easier way to do it. That is the crap that Pertronix hands out. I'll just keep helping people fix the issue at hand.
My method takes about an hour and there are zero permanent changes to the factory harness. It works and has for several here.
It's clean, the tach works correctly afterward and the Pertonix doesn't fail. Six feet of 14 gauge wire, a male and female bullet connector and a Scotchok and is easily and completely reversible.
I had a old loom around, so I did a mock up of how or where to splice the new 12 V wire that runs out to the Pertronix.. Splice is done on the red / green stripe wire..
"The going thing" is this how you did yours ?
That will absolutely work as well. I tried to stay away from the wires that carry a load off the ignition switch connection. I used the red wire that goes into the tach just before the bullet connector. (It gives 12V constant power. The resistor wire is on the other side ( drivers side connection of the tach). It gives 12V constant power.)
OK, so the 2 Tach wires are the Red / Green stripe that loops from the ign switch and has a female connector and the Pink / Red has the bullet connector.. This is the one you use to splice into for the 12V feed ?
(just noticed the terminal popped out of the Ign Switch block)
As a fact I wouldn´t start a thread if I´m not sure that a Pertronix 3 will definetly destroy the tach of a GT500 if you wire it the wrong way, I knopw a bunch of germans that learned this lesson the hard and expensive way on 67/68 FE Mustangs. Check the FE and Mustang Forums and you will see with the tach you need a special solution. The instruction is only working for cars w/o a tach. And I only want to know how people here are solving this problem.
If some of you know the tach rebuilders they can tell you that the most of the repairs they have are because of msd/pertronix that were wired wrong. I checked under the dash yesterday of my GT500 and what have I seen there wooooow there is a MSD Tach Adapter and that one was installed in the late 80s because the owner then installed the pertronix, and my tach is ok. Maybe I take it out and do the installation more original style because I like to keep things clean and original.
The Going Thing is correct with his statement about the wiring etc.
I would say we should make a drawing with some pictures for this thread how to make it correct, then everybody who is doing a search can use it. It´s not uncommon that people take their orignal fomoco distributor and add a pertronix 3, its a nice celan solution vs msd with their boxes etc.
Kent: Had I known I would have taken pictures while the cluster was out to make it simple enough for a Caveman to do it. It will destroy the tach if wired incorrectly. Yes, two well known to this forum told me exactly that. It's why I made sure it was wired correctly before the cluster was installed. I plugged the tach leads together so it would run until I had completed the interior.
The same person telling me I'm wrong told Randy Gillis the same thing. Most of you know Randy Gillis, he needs no introduction here nor his qualifications.
I know most of us try to hide modifications to our Shelbys. After looking at the abortion of a schematic offered by the empty heads at Pertronixs I found a simple way to wire them and hide the modification with the exception of the 14 gauge wire running from the tach lead under the dash to the red wire for the module in the distributor. I taped it to the lead running to the coil and it is in the clips on the valve covers which makes it hard to see. There's no real need for a schematic.
It's one wire. The balance is wire per instruction. The black lead from the Pertronix goes to the negative terminal of the coil. The Ford harness wire slips right on the terminal as it was.
I would recommend the II, as it no longer requires the dwell to be set. The rev-limiter is really the only advantage of the III unless you're using it as a trigger for an MSD box.
If pictures of the firewall forward and coil wiring pictures will help I'd be glad to provide them. I am not planning on removing my cluster for anything at the moment, so that would be more difficult to provide.
Being this has been such a confusing factor for many, I wish I would have done a step by step .
This is great information as I am having my distributor rebuilt now with a pertronix III (to gain the rev limiter feature) and I would very much appreciate a schematic even if it's hand drawn. My car has had previous modifications and it didn't have the factory tach so I'm adding all the Shelby parts and can't really count on anything that's there being correct. Help me out with a drawing if you can.
Just to be clear I was planning to use the Pertronix coil if that makes a difference in the wiring.
I had this diagram stored in my Shelby stuff but don't remember where it came from. Is this diagram correct? If used with the standard yellow top coil will this result in correct tach readings?
Anyone have a similar diagram for the 65 GT350 tach?
I actually had this stored in my GT350R folder but that doesn't mean a lot. I don't know what "Faira" tach means. I don't remember hearing that term anywhere else.
That diagram is correct however I always tie in at the bullet connector so that no wires need to be cut. It won't affect the tach at all if wired this way - the correct way.
Quote from: mlplunkett on December 04, 2020, 04:19:50 PM
I had this diagram stored in my Shelby stuff but don't remember where it came from. Is this diagram correct? If used with the standard yellow top coil will this result in correct tach readings?
Quote from: mlplunkett on December 05, 2020, 09:51:38 AM
I actually had this stored in my GT350R folder but that doesn't mean a lot. I don't know what "Faira" tach means. I don't remember hearing that term anywhere else.
Faira is the mfg name for the 66 GT350 tach.
So will this diagram work for the 65-67 tachs including the R Model instrument package?
Quote from: Royce Peterson on April 20, 2020, 12:40:59 PM
Yes indeed. The Pertronics coil is lower resistance than the stock coil. So it gives a higher output to the plugs but ruins the performance of the tachometer.
Personally I prefer using the stock yellow top coils.
Quote from: oldcanuck on April 20, 2020, 09:47:03 AM
I wired per the instructions, but I replaced the old non-original coil with a new Pertronix Flame Thrower coil as I thought that is what was required for the HEI ?
Is that were I goofed....... ?
If I swap back to my stock coil on my Pertronix I conversion, will it correct my low reading tach ?
Thanks All.
Quote from: oldcanuck on December 14, 2020, 08:45:57 AM
Quote from: Royce Peterson on April 20, 2020, 12:40:59 PM
Yes indeed. The Pertronics coil is lower resistance than the stock coil. So it gives a higher output to the plugs but ruins the performance of the tachometer.
Personally I prefer using the stock yellow top coils.
Quote from: oldcanuck on April 20, 2020, 09:47:03 AM
I wired per the instructions, but I replaced the old non-original coil with a new Pertronix Flame Thrower coil as I thought that is what was required for the HEI ?
Is that were I goofed....... ?
If I swap back to my stock coil on my Pertronix I conversion, will it correct my low reading tach ?
Thanks All.
Royce, somebody..... please. I dont want to try this and end up hurting something on the car.
Thanks for your help.
Quote from: oldcanuck on December 30, 2020, 08:53:50 AM
Quote from: oldcanuck on December 14, 2020, 08:45:57 AM
Quote from: Royce Peterson on April 20, 2020, 12:40:59 PM
Yes indeed. The Pertronics coil is lower resistance than the stock coil. So it gives a higher output to the plugs but ruins the performance of the tachometer.
Personally I prefer using the stock yellow top coils.
Quote from: oldcanuck on April 20, 2020, 09:47:03 AM
I wired per the instructions, but I replaced the old non-original coil with a new Pertronix Flame Thrower coil as I thought that is what was required for the HEI ?
Is that were I goofed....... ?
If I swap back to my stock coil on my Pertronix I conversion, will it correct my low reading tach ?
Thanks All.
Royce, somebody..... please. I dont want to try this and end up hurting something on the car.
Thanks for your help.
The Pertronix is designed to work with or without the stock coil. If all things are equal and your tach is working now although with a low reading then there is no reason to think you will hurt the tach if you change back to the stock coil. It may not change things given the tach may already be hurt but no reason to think it will make things worse. The tach typically gets hurt if wired up wrong in the schematic. I hadn't heard of a situation like yours before. I hope changing out the coil helps. Keep us posted.
If the tach is reading low with an aftermarket coil it (the D'Arsenval movement in the tachometer) likely has lost some magnetism over the years. The stock coil has a higher resistance than most aftermarket coils that I am aware of. Higher resistance = lower current in the circuit. Lower current means lower RPM reading. The tachometer in 1967 - 68 is in series with the coil, it is in effect an amp meter that reads in RPM.
Quote from: oldcanuck on December 14, 2020, 08:45:57 AM
Quote from: Royce Peterson on April 20, 2020, 12:40:59 PM
Yes indeed. The Pertronics coil is lower resistance than the stock coil. So it gives a higher output to the plugs but ruins the performance of the tachometer.
Personally I prefer using the stock yellow top coils.
Quote from: oldcanuck on April 20, 2020, 09:47:03 AM
I wired per the instructions, but I replaced the old non-original coil with a new Pertronix Flame Thrower coil as I thought that is what was required for the HEI ?
Is that were I goofed....... ?
If I swap back to my stock coil on my Pertronix I conversion, will it correct my low reading tach ?
Thanks All.
Maybe I wasn't clear..... the Pertronix I was installed new July 2020 with a new Pertronix Blaster coil. I have run the car appx. 1000 miles since the installation.
The installation instructions included, were used. The system works well, but my tach seems to be reading 3-400 rpm low.
My question is.... if I put my previous stock coil back in, will this solve my rpm reading ?
The Pertronix coil is lower resistance than a stock coil so it will read a higher RPM. If your tach is reading low with a Pertronix coil installing the stock coil will cause it to read even lower. Higher resistance = lower RPM indication. Lower resistance = higher RPM indication. No it is not going to have the effect that you desire.
Why not try it for yourself? We are talking about less than 5 minutes work.
Quote from: oldcanuck on December 31, 2020, 06:24:36 PM
Maybe I wasn't clear..... the Pertronix I was installed new July 2020 with a new Pertronix Blaster coil. I have run the car appx. 1000 miles since the installation.
The installation instructions included, were used. The system works well, but my tach seems to be reading 3-400 rpm low.
My question is.... if I put my previous stock coil back in, will this solve my rpm reading ?
My thoughts are run stock coil, petronix 1. Ran this in several cars with stock tach and never an issue. No problems with enough voltage to run system even with resistor wire or tach operating properly.
Thank you guys.... I will give it a try and report back.
BG