Melting wires, simple question

[bbodie52]

Some high output high performance ignition coils have a very low primary resistance. It may almost look like it reads zero ohms if you don't check it carefully. The standard Delco coil has a 1.42 ohm Primary resistance. Most aftermarket coils have either 1.5 ohm or 3.0 ohms Primary resistance. These coils will work with ignition points or most breakerless electronic ignition systems, like the Pertronix Ignitor or FAST (formerly Crane Cams) XR700. Some ultra high output high performance coils increase their spark plug (secondary) output voltage by greatly reducing the Primary resistance to something like 0.6 ohms or less. This may be seen in the Pertronix FlameThrower II coil and similar racing coils. These coils are designed to be used with no external ballast resistor or resistor wire, and they draw a lot more current through the Primary coil winding. They cannot be used with ignition points, as the high current would cause excessive arcing and burning of the points switch contacts and would quickly destroy them. High output coils with 0.6 ohms or less must be controlled with special electronic ignition modules like the FAST XR3000 or the Pertronix Ignitor II, both of which use a special high current switching transistor circuit that can handle the high current flow through the high performance, coil that is designed with a very low primary resistance.

The ultra high-performance coils are overkill on any Corvair, including the turbocharged Corvairs. The low RPM operation and moderate compression ratio of 9.0:1 or less does no overtax the spark plugs and ignition systems. Even the turbocharged Corvair engine will do just fine with a standard ignition coil. The electronic ignition controlled distributor will provide better, more reliable operation by eliminating ignition points and substituting a transistorized switching system — typically using a magnetic or optical trigger in the distributor. A moderate aftermarket coil may be designed to be installed without a ballast resistor wire or external resistor, which can permit a higher secondary spark plug output for improved engine operation. The original design used in Corvairs and many other vintage engines utilized a ballast resistor in the Primary circuit to reduce electrical current flowing through the coil and ignition points. This reduced operating current helped the coil to last longer by reducing heat buildup in the coil, and the lower current also prolonged the life of the ignition points contacts by reducing arcing and burning as the contacts opened and closed. These early systems typically increased the coil primary voltage during cranking and startup by connecting the starter motor solenoid to the coil to bypass the ballast resistor wire and provided full battery voltage during engine cranking. (The bypass boosted the spark plug output of the coil to promote cold engine startup).

Some moderate high performance coils are engineered to be powered by a full 12VDC all the time. Their installation instructions may include removal of the factory ballast resistor or resistor wire to provide a somewhat higher output to the spark plugs. The use of an electronic breakerless ignition system may permit this ballast resistor removal. Be sure to carefully read and follow the aftermarket ignition system installation instructions.

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[NMVair]

So, since I am getting my wire harness today I drove the car this weekend. It did well and the wires didn't get hot. By the way,it's not the coil, I just mentioned the coil because I was asked about modifications. The coil was part of the ignition upgrade.
In any event, I think it may be the heater motor. If it is I'm going to replace the motor and install heavier gage wire for it.

[cnicol]

Options for melted wires in engine harness:
(This is a comprehensive list)

1) Short circuit in Tail/license light circuit. Circuit has overcurrent protection so not likely.
2) Short circuit in Turn/brake light circuit. Circuit has overcurrent protection so not likely.
3) Short circuit in Reverse light circuit. Circuit has overcurrent protection so not likely.
4) Short circuit or overload in Coil/Ignition system - no overcurrent protection - possible reason
5) Short circuit or overload in alternator/B+ main circuit - no overcurrent protection - possible reason

Because 1,2,3 are protected by fuse or flasher, problems in this area would not cause melting.

This leaves #4 or #5 as the potential problem areas.

4) If the replacement ignition coil is of the low-ohm variety and your "electronic ignition" does not include current limiting, that could certainly cause a melt down and this has happened to others. If the harness's resistor wire is shorted to ground, that would cause melting and immediately stop the engine.

5) A short in the alternator or B+ main circuit could also be the source of melting but this would typically be a total meltdown or fire and certainly would not allow subsequent driving.

Re heater motor being the source of the melting. While your heater motor gets its power from the engine harness (alternator and/or battery), the heater circuit has a 20-amp fuse and the engine harness has a 50-55 amp capacity so a defective or oversize heater motor would blow a fuse or melt it own lower capacity 12-gauge wire long before it affected the 10-gauge engine harness.

[NMVair]

Thank You so much cnicol. But I don't think thecwires that melted were 10 gauge. I'm not at my car but my memory says there no larger than 14.

[NMVair]

Ok. I'm pretty sure we'll be able to figure things out but in terms of wires for includingvmy alternator-. It looks like I will need 10 gauge and a 14 gauge, is this correct? And all I will need to know are the colors, and I can pick them up from my local electrical store.

[sethracer]

For reference. With the TSP distributor, I recommend bypassing the stock resistance wire and feeding both the coil and the distributor full battery voltage. I also recommend using ONLY a 3.0 Ohm coil with that set-up. With a battery voltage feed, you will still have plenty of spark output, and you will not be overstressing the internal electronics of the dist. I agree with BBodies52 comments.

[NMVair]

The harness got here yesterday. We will do the job Saturday. Any direction is appreciated.

[Frank DuVal]

10 AWG is RED.

And it looks like the two 14 AWG wires are RED and WHITE. Hey I typed WHITE, but it is hard to read!

This is just to match the most common Delco 10 SI alternator pigtail wire colors. Electrons are color blind...

[bbodie52]

A new engine compartment wiring harness may not match the actual, modified configuration present in your engine compartment. A conversion from a generator (1964) to an alternator requires some modifications, as would the use of an external voltage regulator vs. an internal electronic voltage regulator that is inside many newer alternator designs. A modified ignition system that utilizes a different ignition coil and an electronic breakerless electronic ignition module often requires modifications to the main harness, such as possibly the removal /bypass of the ballast resistor wire. The FAST XR-700 needs the ballast resistor wire to stay, while the FAXT XR-3000 or the Pertronix Ignitor modules are designed for a full 12 VDC power source — bypassing the resistor wire. The use of a 3 ohm ignition coil means bypassing the ballast resistor wire, as it provides the correct 3 ohm Primary circuit resistance internally, and retaining the external ballast resistor wire too would significantly weaken the spark plug output from the 3 0hm coil.

As I mentioned before, the 1963 and earlier engine compartment wiring harness connected to an 8-pin multiconnector. In 1964 the schematic shows a 10-pin connector. Check the main end connector to ensure that it matches the main chassis wiring harness that enters the engine compartment through an opening below the voltage regulator.

I'm not sure if the cause of the original melted wire insulation has been determined. If there is an internal fault inside your alternator, you might have a short to ground. Connecting a new wiring harness to a shorted alternator could damage the new harness! If there is any doubt about the viability of your alternator, it may need further testing before connecting it to the new wiring harness.

Is your alternator internally regulated, or does it utilize an external voltage regulator?

If you discover conflicts and need to resolve any mismatches or modification requirements, just provide the details of your question(s) here and we will try to provide any needed assistance.

Looking at the original schematic diagrams will give a strong clue as to the correct wire gauge for each circuit. Generally it appears that all of the control and sensor wires supporting the external voltage regulator were a thin 20 Gauge, since they actually carried very little electrical current. Note that the main power wire for the alternator was a thicker 10 Gauge, since it carried much-more current to charge the battery and power most of the circuitry throughout the vehicle. As power is distributed throughout the vehicle, the wire gauge can be reduced, as it depends on the current draw from the various devices at the end of each circuit. The direct cable feeding the starter motor carries the most current. The heater fan motor, horns, and headlights draw significant current, gauges and small instrument lights carry only a small amount of electrical current, etc.

LEFT-CLICK EACH IMAGE TO ENLARGE FOR BETTER VIEWING. LEFT-CLICK A SECOND TIME FOR MAXIMUM ENLARGEMENT...

[Vairone]

Some high output high performance ignition coils have a very low primary resistance. It may almost look like it reads zero ohms if you don't check it carefully. The standard Delco coil has a 1.42 ohm Primary resistance. Most aftermarket coils have either 1.5 ohm or 3.0 ohms Primary resistance.

Measuring the coil primary resistance with an ohm meter is a good starting point to select the proper coil for the job. Coils are inductors, not resistors, so different measurements are needed, but more difficult to obtain. The primary resistance will not tell you the turn ratio of the coil or the magnetic core strength, but again, coil primary resistance is a good starting point.

The ultra high-performance coils are overkill on any Corvair, including the turbocharged Corvairs. The low RPM operation and moderate compression ratio of 9.0:1 or less does no overtax the spark plugs and ignition systems. Even the turbocharged Corvair engine will do just fine with a standard ignition coil.

Turbocharged Corvairs will see an improvement with a high performance coil, or even better, a high performance ignition system, as boosted operation requires higher spark output.

Be aware that some electronic ignitions [Pertronix Ignitor] shorten the dwell to less than 30 degrees and a performance reduction vs. points, may be noticed.

[bbodie52]

Dwell time is measured in the number of degrees of the distributor’s rotation through which the contacts of the points are closed.

UNDERSTANDING IGNITION DWELL
Kelli Murrow
5 min read
July 21, 2021
https://pertronixbrands.com/blogs/produ ... tion-dwell

Turbocharged Corvairs will see an improvement with a high performance coil, or even better, a high performance ignition system, as boosted operation requires higher spark output.

Be aware that some electronic ignitions [Pertronix Ignitor] shorten the dwell to less than 30 degrees and a performance reduction vs. points, may be noticed.

The above article by Pertronix discusses the issue of dwell in more depth. An ignition coil needs a certain amount of time to develop an electromagnetic field that is adequate to provide a strong spark plug voltage. This time, referred to as dwell, is the amount of time, or degrees of engine rotation, that the points remain closed to build the needed magnetic field within the coil Primary winding. When the points open the magnetic field collapses, which induces a voltage in the coil secondary winding, which in turn is sent via the rotor, distributor cap, and spark plug wires to the appropriate spark plug to ignite the compressed fuel/air mixture in the cylinder. Higher engine RPM means less time with the points closed for that magnetic field to build in the coil Primary winding. If the time is too short, the magnetic field will be reduced and the coil spark plug voltage may be weakened. Also, the amount of pressure present in the cylinder during the compression stroke can affect the spark and "flame front" that ignites the fuel/air mixture. A higher engine compression ratio affects ignition in the cylinder, and boost from a turbocharger can have a similar impact on ignition. A stronger spark plug voltage helps for a better combustion chamber ignition process to produce a good, efficient engine power stroke.

When the points are eliminated and replaced by an electronic circuit controlling a switching transistor, the dwell time is established by the electronic circuitry. The basic Corvair Delco coil has a 1.42 ohm Primary coil that — because of the presence of a 1.8 ohm ballast resistor wire in the Corvair engine compartment wiring harness — does not have a full 12.5 - 14.5 volt system voltage to build the magnetic field inside the coil. Instead, the ballast resistor wire reduces this operating voltage fed to the coil Primary winding to only about 7 VDC. (This was done mainly to help prolong the life of the ignition points switch contacts as they open and close, by reducing arcing and burning that occurs each time the points open and close).

A well-designed electronic breakerless ignition system, like the Pertronix Ignitor II or the FAST XR-3000, substitutes an electronic circuit-controlled solid-state switching transistor for the ignition points switch. With no physical switch contacts in-play, the switching transistor can handle a higher voltage and more current fed to the appropriate matching high-performance coil. The GM factory ballast resistor wire is normally bypassed when upgrading to a modern electronically-controlled ignition system, and an appropriate matching ignition coil is selected to match the needs of the engine, based on expected engine RPM range, compression ratio, number of cylinders, whether a turbocharger or supercharger is present, etc.

For most Corvairs, a 3.0 ohm high performance igntion coil operating without an external ballast resistor is appropriate for the six-cylinder engine. The Pertronix Ignitor or Ignitor II breakerless ignition module will support the 12 VDC power source and the current drawn through the 3.0 ohm Primary winding. (A Pertronix Flamethrower II 0.6 ohm coil could be used, but only in conjunction with a Pertronix Ignitor II or a FAST XR-3000 ignition control system, as they have a heavy-duty switching transistor circuit that can support the greater amount of electric current that is drawn by the FlameThrower II 0.6 ohm coil. The Pertronix Ignitor or FAST XR-700 cannot handle the high current draw of the ultra low-resistance coil Primary.

I know I have included a lot of technical details here, but as you can see upgrading to a modern electronic ignition system requires careful consideration of a number of factors when choosing all of the upgrade components, their compatibility with the other components used in the final system, and the needs of the engine itself. A mismatch of the components selected, or an incorrect installation, can degrade engine performance or shorten the life of the electronic components. Following and understanding the manufacturer's recommendations and installation instructions are important for a successful outcome.

[66vairguy]

I do appreciate all the information Brad puts out, and most of it is valuable. That said the "3.0 ohm High Performance coil" is a myth. The Corvair 65-66 140HP and turbo engines used a high performance DELCO coil at about 1.3 ohms with the stock 1.8 ohm ballast for a total or about 3.1 ohms. Bob Helt and others tested it against some of the "HI-OUTPUT" coils around the 1990's and the CORVAIR COIL was the superior performer!! Sadly it is NOT produced now. I've seen the coil number on Corvette reproduction coils (same coil as Corvair), but being reproduction it is difficult to determine if it really works as well as the DELCO coil.

There is often confusion about 3.0 ohm coils, but they simply have an INTERNAL BALLAST and there is no proof they perform any better that Corvair 140HP/turbo coil and ballast (that has a total 3.1 ohms)

As Brad said the DWELL is the time the points are closed. Simply put take a 6 cylinder and you get six 60 degree segments for ONE distributor rotation or 60 degrees between cylinder firing. Keep in mind the distributor moves at HALF the engine speed. So the crankshaft moves 120 degrees between each cylinder firing (4 stroke). If the points are closed 30 degrees out of 60 degrees then you have a 50% duty cycle or closed half the time, open half the time. NOW - it has been known for for many decades as the engine speeds up the points closed/open time gets shorter, although still the same percentage of degrees.

If you optimize for low engine speeds then the spark is inadequate at higher engine speeds. If you optimize for higher engine speeds, then the coil tends to overheat at lower engine speeds!!! What to do? Back in the early to mid 1900's there were actually some creative mechanical dwell control schemes for racing, but unreliable for daily cars. THEN GM developed the HEI system. TWO DWELLS!! At low engine speeds the points closed time is shorter to use maxium voltage without over heating the coil. Above a certain RPM the HEI selected a greater dwell (remember as engine speed increases dwell time is less) that produced adequate output using full voltage to the coil but the reduced time of higher RPM prevented the coil from overheating!! Wonderfully simple, elegant, and reliable thanks to modern electronics. That said, the GM patent expired and now there are a lot of CHEAP imitations that have issues.

Finally the naturally aspirated Corvair engine gets by fine with the ballast and a GOOD 1965 Chevy 283c.i. V8 engine coil. If you have a turbo then you might as well go to computer control and coil packs. Superior to a mechanical distributor and coil. Just my

[NMVair]

That all stands to reason. I guess the big question now is, is my Stinger ignition one of the cheap ones? I've been really happy with it, I mean it seems to be consistent. No dealing with points etc etc. But frankly, I've pushed my 140 and it's responded well, but I wonder if on one of those occasions wires didn't get hot. A friend said the coil would have gotten hot and would give up the ghost.
And would this overheating manifest it's self on the brown wire coming out of the alternator?

[cnicol]

The only things that could cause the alternator "brown" wire (#1) to melt would be 1) Short to ground somewhere between the alternator and the GEN/FAN light in the dash or 2) Another wire in the harness melting for some reason and shorting the brown wire to ground. The brown wire (GEN/FAN light & Alternator "turn-on" signal) is not fused so any short results in a meltdown.

PS: On rare occasions, there's a problem in the tunnel where the clutch or parking brake cable cuts into the harness and shorts wires. I'm not saying this is the problem but it is a possibility.

NMVair: Did you receive the PM I sent at your request?

[NMVair]

Thanks, cnicol, I'm tech challenged but I'll check. We will also trace that wire to the dash.

I have a 64 service manual. Since I have a 68 140 in the car should I get a late model diagram?

[66vairguy]

That all stands to reason. I guess the big question now is, is my Stinger ignition one of the cheap ones? I've been really happy with it, I mean it seems to be consistent. No dealing with points etc etc. But frankly, I've pushed my 140 and it's responded well, but I wonder if on one of those occasions wires didn't get hot. A friend said the coil would have gotten hot and would give up the ghost.
And would this overheating manifest it's self on the brown wire coming out of the alternator?

Seth already recommended using a 3.0 ohm coil with NO ballast and that should NOT cause a problem with wiring. It will also keep the HEI module from being stressed. So if you like your Stinger and it works, then fine.

Craig summed it up well about the wiring at the alternator. I've run into a few EM wiring issues when folks convert to an alternator, either external regulated (10DN) or internally regulated (10SI). Just my opinion --- but I'd find someone with auto/Corvair wiring experience to help sort this out. I usually help folks in my club no charge for labor. Maybe you'll get lucky and find someone willing to help.

As I like to say -- "Good wiring is cheap fire insurance".