Burning up Coils

[LiLMike 42]

Got a problem that is driving me crazy. I have a 100 amp alternator and an electronic module instead of points. Started out with a Mallory E-Coil with an internal bleeder resistor. Ran car for awhile and it burnt up along with the electronic module in the distributor.Tried another one with the same results. Switched to an oil filled coil with a relay in place of a bleeder resistor. That coil burnt up. Replaced with another regular coil and added a bleeder resistor. Ran fine for about 3 weeks and car just died sitting at a light. I now have a bad electronic module in the distributor. The only thing I can come up with is moving the coil/distributor circuit to an isolated circuit with it's own fuse. Any suggestions?

[Mach1 Driver 560]

Ford did not put a fuse in the circuit because they didn't want to strand people by adding another part and increasing the likelyhood of a connection failure. If you look at page 1 of the schematic in the post "A REAL Schematic" here in the "How Tos" section, you will note that a stock coil is not designed to run 100% of the time on 12v. With charging at 14.5v, the coil will be at about 10.8v. That being said, I don't know what your aftermarket coil is designed to do or how the system is wired.

Unless you've got some wires crossed somewhere, the alternator issue is not related to the ignition issue. Charging is on page 2 of the schematic, and is pretty simple.

[LiLMike 42]

2 hours ago, Mach1 Driver said:

Ford did not put a fuse in the circuit because they didn't want to strand people by adding another part and increasing the likelyhood of a connection failure. If you look at page 1 of the schematic in the post "A REAL Schematic" here in the "How Tos" section, you will note that a stock coil is not designed to run 100% of the time on 12v. With charging at 14.5v, the coil will be at about 10.8v. That being said, I don't know what your aftermarket coil is designed to do or how the system is wired.

Unless you've got some wires crossed somewhere, the alternator issue is not related to the ignition issue. Charging is on page 2 of the schematic, and is pretty simple.

I have an AAW wired car and it was running fine until I replaced the motor. I do have only 10.9 volts at the coil going to the distributor. That is what is puzzling. Everything seems to check out as it should but either the coil or electronic module craps out after a couple of weeks or so. It just runs fine for awhile and then just dies. Wondering if there is some sort of power surge or something.

[Mach1 Driver 560]

A loose connection (power or ground) that causes the power to come on and go off repeatedly could create surges that may harm the electronics, but not the coil. About the only thing that would affect the coil is heat, or just bad luck... excluding high voltage or mechanical damage. I assume the alternator (when it works) isn't putting out excessive voltage?

[LiLMike 42]

The alternator is good and has an internal regulator. The coil is mounted on the firewall. The car is driven to car shows and cruise-ins when it is running. The last time the coil burnt up was when it was ideling for a long time. Removed the coil and the top was separating from the body of the coil. Put in one of those Master Blaster coils and bleeder resistor in. Car ran and was driven for about 3 weeks and then just died at a light the other day. It took out the electronic module in the distributor. Going to replace the module and check the wiring.

[LiLMike 42]

Thanks Mach1 Driver. I found the problem. The coil/Distributor circuit was wired wrong. Corrected that and it starts great with 12vdc at the coil and drops down to 9.8 vdc when running.

[1969_Mach1 333]

9.8V when running sounds about right for a stock ignition coil and points.  Be certain that is correct for the coil and Pertronix setup you are using.  Many use 12V.

[Midlife 814]

1 hour ago, LiLMike said:

Thanks Mach1 Driver. I found the problem. The coil/Distributor circuit was wired wrong. Corrected that and it starts great with 12vdc at the coil and drops down to 9.8 vdc when running.

For future reference, what did you find mis-wired?  For folks who see the same problem in the future, we can certainly use this information!

[69ShelbyGT350H 61]

The Pertronix Ignitor units require 12v while running. Most of those who have had failures were still using the factory resistor wire from the ignition switch which drops the voltage. Another issue is not using a matching FlameThrower coil with 1.5 ohm resistance, though Pertronix also states "The Ignitor III is compatible with coils having a resistance of 0.32 ohms or greater". All other resistors (including the resistor wire) should be removed. Pertronix still warns to NOT leave the ignition on while not running the engine for extended periods of time with the I and II units. However, I do not see this warning with the Ignitor III unit. The Ignitor III needs to be powered on to set the internal RPM limiter.

http://www.pertronix.com/docs/instruction-sheets/1181.pdf

http://www.pertronix.com/docs/instruction-sheets/1281.pdf

 

Sorry, I'm not trying to derail if you are not using a Pertronix Ignitor unit in your distributor.

 

 

[1969_Mach1 333]

5 hours ago, 69ShelbyGT350H said:

The Pertronix Ignitor units require 12v while running. Most of those who have had failures were still using the factory resistor wire from the ignition switch which drops the voltage. Another issue is not using a matching FlameThrower coil with 1.5 ohm resistance, though Pertronix also states "The Ignitor III is compatible with coils having a resistance of 0.32 ohms or greater". All other resistors (including the resistor wire) should be removed. Pertronix still warns to NOT leave the ignition on while not running the engine for extended periods of time with the I and II units. However, I do not see this warning with the Ignitor III unit. The Ignitor III needs to be powered on to set the internal RPM limiter.

http://www.pertronix.com/docs/instruction-sheets/1181.pdf

http://www.pertronix.com/docs/instruction-sheets/1281.pdf

 

Sorry, I'm not trying to derail if you are not using a Pertronix Ignitor unit in your distributor.

 

 

I've never personally uses anything from Pertronix.  I have read from several places basically everything you just stated.  A lot of people like the Pertronix stuff so they can keep the stock distributor look.  But I've always thought if converting to electronic ignition, go all the way instead of just using something that is a points replacement.  Use Duraspark if you want to stay with Ford or use something from MSD or somebody else for aftermarket.

[Mach1 Driver 560]

A word of caution; I was warned by Chris Straub (who makes custom cams) that most of the aftermarket distributors now use Chinese gears that tend to eat the cam. I believe the only gear he recommended was made by Comp Cams. I looked for the information for 20 minutes and gave up- Barnett will know if he drops by.

[69ShelbyGT350H 61]

3 hours ago, 1969_Mach1 said:

I've never personally uses anything from Pertronix.  I have read from several places basically everything you just stated.  A lot of people like the Pertronix stuff so they can keep the stock distributor look.  But I've always thought if converting to electronic ignition, go all the way instead of just using something that is a points replacement.  Use Duraspark if you want to stay with Ford or use something from MSD or somebody else for aftermarket.

Honestly, the message was for the OP, LiLMike as he did not state what electronic ignition he is using, just that his coil voltage drops down to 9.8v. I have the Ignitor III and Flamethrower, and want that stock look. 

[LiLMike 42]

I have a Mallory distributor that was upgraded to their electronic ignition. I have an AAW wiring harness so no restive wire. The problem was that the red wire from the distributor went to the fuse block for a constant 12vdc instead of going to the coil. It never dropped down to 10.8 vdc or 9.8 vdc and that is why I kept burning up coils and electronic modules in the distributor. Connected the red wire from the distributor straight to the coil and everything works great. It evens starts faster.

[1969_Mach1 333]

19 hours ago, 69ShelbyGT350H said:

Honestly, the message was for the OP, LiLMike as he did not state what electronic ignition he is using, just that his coil voltage drops down to 9.8v. I have the Ignitor III and Flamethrower, and want that stock look. 

No problem.  I understood the message was intended for the OP.