 Mallory Unilite® and E-Spark® Module Testing
 The Mallory Unilite® and E-Spark Ignition Modules are highly accurate, reliable, and simple ignition triggers and amplifiers. The self-contained module consists of an integrated photo coupler, a signal processor, and a power switch. Every time the special shutter wheel rotor stops the infrared light from reaching the photo coupler, the electronic circuitry energizes the ignition coil. When the shutter wheel allows the infrared light to reach the photo coupler, the electronic circuitry allows the stored energy in the ignition coil to discharge to the spark plugs. No adjustments are ever necessary.
Order a Replacement Module part #MAL-6100M
NOTE: We only offer the E-Spark module as a replacement.
One of the statements we hear from customers when they call us about testing/replacing their Unilite® module is that they have read on various web forums that the Unilite® is an unreliable POS. We can tell you that the people posting those comments should probably not be working on their vehicles unsupervised. These people are blaming the affect (a blown or damaged module) instead of what actually caused the module to fail.
 I regularly use the following analogy when speaking to our customers about module reliability: If you were to purchase four brand new tires and then knowingly drive through a pile of steel and all the tires go flat, would you blame the tires as being junk? The reply that is given 100% of the time is "of course not!". The driver was obviously an idiot. So, why do people find it so easy to blame an ignition module? The easy answer is lack of understanding of the product. It is easy to blame something that you know nothing about.
The modules cannot really kill themselves, so you have to try to find out what caused the failure. We have customers that have used the same module for 20+ years and others that have killed three on a Saturday afternoon. The guy that killed three purchased two rebuilt alternators from a typical chain store and both had cheap (cost savings), sticking diodes in them, causing a voltage dump to ground. I endured considerable screaming, cussing, and insults, yet I finally got him to agree to take the alternator(s) to a local rebuilder on Monday for testing. NOTE: The basic bench testers in the parts stores cannot test for sticking diodes or a voltage dump. A fast oscilloscope is required. He found out after the units were tested that they were sending a 140+ amp spike to ground every time he turned off the key. This explained why the engine would start once with the new module, but never again. Replacing the diode in the "new" alternator solved the problem.
NOTE: It is possible to have intermittent problems with the Mallory modules. Say the module has been damaged, but not completely dead. You could be driving along and the engine dies. You check everything out, see nothing wrong, and get back in the vehicle and it starts right up. This could happen daily or just once in a while. Test the module and it will most likely fail testing. This is almost a benefit in that in some instances it does not just die and leave you stranded. It is giving you a warning sign that you need to act upon. REPLACE THE MODULE!
Step by Step Module Testing - Unilite® and E-Spark®
Tools Needed: Volt Meter or DMM, Credit Card or piece of thin cardboard
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Important: If you are using a CD amplifier (Mallory Hyfire®, MSD, Jacobs, Accel 300+, etc) on your vehicle you must first unwire it from the system or you will not get a valid test result. You can bypass some of these with a supplied connector, but otherwise you MUST unwire it. After removing the amplifier you will need a ballast resistor installed in the system to prevent killing a good module (if you attempt to start the engine). Follow your distributor instructions for proper installation.
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Remove distributor cap and rotor.  The Mallory rotors are usually on pretty tight, but it is only a press fit. You will be able to get the rotor off by firmly pulling straight up, though in all honesty it may hurt a bit.
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Turn the ignition key ON and use your DMM (Digital Multi-Meter) to measure supply voltage. First check voltage at the POSITIVE side of the coil by connecting the black lead of your meter to a good ground (engine block) and the red cable to the coil. The meter should read close to battery voltage. Now check voltage at the NEGATIVE side of the coil by moving the red lead from your meter to the negative side of the coil. Your meter should also read close to battery voltage. If everything is good here, continue. If you do not get "close" to battery voltage you need to make sure there is not a power supply problem. Take a jumper wire from the positive post on your battery to the positive side of the coil. If you still do not have a reading close to battery voltage at both sides of the coil the module is energizing the coil when it is not supposed to be doing so, replace the module.
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With the DMM still connected to the negative side of the coil you are going to watch the meter while blocking the optics on the module with your credit card. Placing the credit card or other device between the towers on the module blocks the optics. When the optics are blocked the readings on your meter MUST drop below 2-volts. It may be just for an instant, or it may hold below two volts until you unblock the module. Either is OK. But if the voltage does not drop below 2-volts the module has been damaged and must be replaced.
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Unblocking the module after step #4 and the voltage reading on your meter MUST return to battery voltage. If the voltage does not instantly jump back up, the module must be replaced.
EXPLANATIONS:
Based upon the test procedure above we can come to a few conclusions.
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If the battery voltage is not initially present you have either an electrical problem prior to the coil (ignition switch, low battery, etc), or the module is charging the coil when it is not supposed to. The module has been exposed to voltage spikes or installation errors.
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If the voltage does not drop when the optic is blocked the module is "open" and was also possibly caused by a power surge, excessively high resistance in the plugs or plug leads, or improper grounds. Replace the module!
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When the voltage always stays below 3.0 volts it means that the module has been spiked by high voltage or amperage, lack of a ballast resistor (if not using an amplifier box), or the wiring was incorrect. Replace the module!
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If the voltage only drops to 3-4 volts you will get a noticeably weak spark. This is also caused by poor grounds, or a power spike. Replace the module!
POSSIBLE CAUSES:
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Faulty charging system (stuck or shorted regulator/alternator), or high amp single wire alternators with a cheap diode.
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Ineffective or inadequate vehicle grounds. The module brown wire must be connected to the engine block. The vehicle grounds should consist of: Battery to Engine; Battery to Body; Engine to Frame; Engine to Body; Body to Frame
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Trying to start the engine using a battery booster-charger. Most of these have very dirty electrical signals which cause power surges or spikes. Disconnecting the battery, charging it, and then reconnecting it is the only correct way
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Using non-suppression plug wire leads. You must use suppression core type plug wires, no solid core wires (stainless steel or copper). Spiral core is best, but carbon core will also work.
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High amp stereo equipment that is not properly grounded or the vehicle grounds have not been updated to handle the added capacity.
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Direct shorts in the vehicle's electrical system
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Welding on the vehicle while the distributor harness is connected.
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Faulty starting system (excess starter drag, not enough voltage/amperage getting to the starter, worn brushes/armature).
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CB radio spiking on mic click into electrical system (typically only on power modified CB radios).
A Few Tips and Lesser Known Facts?
The Mallory Unilite® and E-Spark® does require a drop in voltage for the trigger side of the module even though the power supply side can handle 14+ volts. Even though the ballast is wired inline to the positive side of the coil it is actually dropping the voltage to the negative side of the coil (trigger side). This means that you MUST have ONE of these installed:
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The correct ballast resistor. Mallory #MAL-700 is the best, but another ballast of compatible specs is also acceptable. <or>
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OEM resistance wire in the factory wiring harness <or>
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Internally resisted ignition coil (cannot be used with external amplifier). <or>
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Ignition amplifier like the Mallory Hyfire® series boxes.
On applications that are not using an ignition amplifier you can verify that your system has the correct resistance by connecting a volt meter to the negative side of the coil with the engine running at idle. The measured voltage should be roughly 8-9 volts.
If you are using an ignition amplifier you do not need a ballast resistor, but you should keep one handy. If you ever need to bypass or remove the amplifier you will need a ballast to prevent damage to the module.
Anytime you do anything electrical on your vehicle, no matter what, you should unplug the 3-wire connector at your distributor. This will guarantee that you do not spike the module while working on your vehicle. Remember, it is not the module killing itself that causes failures. It is some other component or human error that kills it.
NEVER try to boost start your vehicle using a battery starter/charger. The dirty power supply and excess amperage can and will damage your ignition module. Disconnect your distributor harness, disconnect and fully charge your battery, then reconnect everything and start the vehicle. If you own a newer computer-controlled vehicle, this is the same procedure recommended by the vehicle manufacturers to prevent ECM damage.
If you want to add some "protection", but not a guarantee to prevent a voltage spike taking out your module, order and install the Mallory Circuit Guard, part #MAL-29371. This component plugs inline on your 3-wire distributor harness and provides two features. The first is a signal filter that cleans up dirty power signal that occurs from dirty connections, or dust in the alternator. Think of this like a rabbit ear antenna on an old television set. They never give you a clean picture, but it takes away some of the snow. On your vehicle this takes away some of the peaks in a dirty signal. The second benefit is a compact, yet tough capacitor that is designed to absorb power spikes, and prevent them from getting to the module. It does absorb some spikes, but is not a guarantee. A decent sized spike will still get through. This is not a replacement for laziness in finding the cause of module failures. This component is inexpensive insurance to prevent module damage.
We recommend having a spare module on hand the same way you have a spare tire or fuses. The Mallory E-Spark® module is an inexpensive replacement for the Unilite (though they are virtually identical), but the E-Spark is even a better module. For reference, the Unilite® or E-Spark® modules are no more or less sensitive that a GM HEI, Ford Duraspark, or other brand ignition modules. They just never bother to tell you the causes of failures, they merely hold out their hands for you to drop some $$$ on a new module with no explanation.
You may or may not know this, but the Mallory Unilite® and E-Spark® modules are both a trigger and coil driver/amplifier. You are not required to use an external amplifier unit. But, if you are using an amplifier and it fails you can easily bypass the amplifier and still get yourself home (you would need a ballast resistor). On other brand ignitions you are stranded until you replace the external box.
You need to using the correct coil with your Mallory Ignition. Without getting into details here, you can take a look at our Coil Selection page to assist you in your selection. Think of a coil like your shoes. You would not wear rubber sandals to climb Mt Everest, nor would you wear Sorels to cross the Mojave desert. You choose a coil to match how you are going to use the vehicle and the operating range of the engine, combined with any other components that may affect your choice (such as an amplifier).
Plug wire selection is also important and we have a tech page that explains selection in detail. You need a certain amount of resistance in your plug wires to prevent voltage leaks from the coil. Too low a resistance causes voltage leaks which lead to lost power, misfiring, and more. Too much resistance in the plug wire leads also causes lost power and performance. Plug wire resistance is measured in "Ohms per foot".
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