LiLMike 42 Report post Posted November 3, 2016 I have a 69 Mach 1 with a 393 Stroker. I have a Mallory distributor with their electronic internal ignition, the pertronix style. I have a 100 amp alternator with an AAW wiring harness, hence no resistive wire. I have burnt up 2 solid state coils supposedly with internal resistance. When I put an old oil bath coil in it fires right up. The solid state coils run about an hour and the go out. Seems like there is a voltage spike or something. I'm scared to put a bleeder resistor in because if that goes then I'll be changing that on the side of the road. Would like to know what the problem is. I always thought that the bleeder resistor was to protect the points, which I do not have. The old alternator was doused with antifreeze when a heater hose blew and I am changing that out but the old one reads good but the I can't see a momentary voltage spike. Any ideas on what I should do next? Thanks Mike Quote Share this post Link to post Share on other sites
1969_Mach1 333 Report post Posted November 3, 2016 First, you simply need to know what voltage your coils are designed to work with, 12V, 9V, 6V? Many coils need an external resistor (ballast resistor) in the run circuit to the coil to drop the voltage supplied to them when the engine is running. Even with an electronic ignition system. The crank circuit feeding the coil bypasses any external resistor (ballast resistor) to supply 12V to the coil during cranking. Quote Share this post Link to post Share on other sites
danno 128 Report post Posted November 7, 2016 If you can run your car for an hour before they blow, that is a symptom of it running too hot. It will run too hot if it has too much current. It can have too much current if it has too much voltage. A dropping resistor will solve that problem, if that is what it is. If your alternator is a single wire version, that can also be a contributor to the problem. One way the single wire alternators work is that they turn themselves on and off all the time. When they are off, they are measuring the voltage on the battery. Then they turn on, and supply an output voltage that is necessary to run the car, based on the voltage it measured when the alternator was off. If the battery connection is weak (or battery cables are bad), then the alternator can be putting out a higher than usual voltage. This higher voltage might be ok for your battery, but it could be overheating your coil. If the coil is mounted in the factory location (on the intake manifold) it is typically quite hot anyway. The way to find out if this could be it is to run 2 wires from your coil to inside your car. Hook up a voltmeter to the wires, so you can monitor the voltage directly on your coil when the motor is running. It will probably be a higher voltage at higher engine speeds. You need to find out what the voltage on the coil is shen the car is running. The odds are a resistor could be added, it will not hurt. Resistors are very reliable, so if chosen and used correctly, it should be fine. The last suggestion would be to contact the coil manufacturer. Maybe they have suggestions? Quote Share this post Link to post Share on other sites
