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Low Voltage
Retro Rockets is an authorized PerTronix dealer.


Ignitor Troubleshooting
Low Voltage
and /or Bad Ground

     We occasionally get Ignitors sent back from customers as faulty.  In the great majority of cases the unit checks out fine indicating there is something amiss with the vehicle.  The most common reasons for an Ignitor not to work are low voltage or a bad ground (earth).  If the red wire is connected to the coil + terminal the voltage there is usually reduced by a ballast resistor or a resistor wire from the ignition switch.  Voltages over 7.5 V will fire an Ignitor in a 12 V system.   However, the voltage can be lower if the resistance in the circuit is higher than it should be resulting in misfires or no spark at all.  This can be caused by loose electrical connections, corrosion at electrical connections or deterioration of a resistor wire due to age or neglect.  There could also be a drop in  voltage due to the load from the starter when the engine is cranking.  If the battery is weak to begin with, voltage may drop below what is required for the Ignitor to function properly.  In cases of low voltage the red wire should be connected to a full 12 V source from the ignition switch as mentioned in the instructions.  The power source must come through the ignition switch so that there is no power to the Ignitor when the engine isn't running.  If there is power to the Ignitor when the engine isn't running and the engine happens to be stopped in a position analogous to points closed, the Ignitor will continue to try to charge the coil.  The current in the Ignitor/coil circuit will have no place to go except into heat.  This could damage the electronics in a standard Ignitor.  The Ignitor II has an automatic shut off feature to prevent any damage under these circumstances.

     Another possible cause for a problem with an Ignitor is if there is a bad ground (earth) between the breaker plate on which the module mounts in the distributor and battery negative (or battery positive in a positive earth system).  With a digital ohmmeter  set on its most sensitive scale, measure the resistance between the Ignitor mount plate and the battery negative post on a negative ground system or the battery positive post on a positive ground system .  Measure to the battery post itself, not the connector on the ground cable.  If it is 0.2 ohms or more, you have a bad ground.  Check for corrosion at the connections of the ground strap between the breaker plate and the distributor housing, and also at the battery itself or where the negative battery cable attaches to the block.  Another possible resistance source is the distributor hold-down clamp which is the electrical connection between the distributor and block or intake manifold.  If engine parts have recently been painted there may not be a good ground.  There is typically a small ground strap between the points plate and the distributor housing.  Be sure that is attached securely and free of corrosion at the contact areas.  0.2 ohms may sound like a negligible amount of resistance, and in a steady state circuit it often is.  But in an ignition circuit where the current is switched on and off many times a second, the transient effects of the 0.2 ohms are significant and can prevent an Ignitor from firing normally.  As the chief engineer at PerTronix says, "If you don't have a good ground, you might as well go in and watch television."


Contact Information

Postal address:
Retro Rockets, P.O. Box 200, Norfolk, CT 06058
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