Frequently Asked Questions - FAQs

Q: How come a ballast resistor is now needed after all of these years of offering the Indigo Ignition Kit without one?

A: That is a good question. I am still not convinced that one is needed when operating an Atomic within all of the proper operating parameters. These parameters include electric system voltage, coil resistance, engine RPM, engine compartment temperature, type of alternator regulator, and normal mode of operation. I personally have never experienced a coil failure but it has recently come to light that some have occurred and the exact reason for the failure(s) is not fully understood. My best guess is that some of the operating parameters are not in the optimum range causing the coils to run excessively hot. The best means of reducing coil operating temperature is to reduce the voltage across the coil and the current running through it with a ballast resistor.

Q: Just what is a Ballast Resistor and what does it do?

A: A Ballast Resistor is an electrical device that is installed in an electrical circuit to provide resistance to the flow of electricity in that circuit. In this specific case, the resistor is installed between the primary voltage source for the ignition coil (the wire that comes from the ignition switch) and the coil (+) stud. With the resistor installed in this manner, the coil no longer sees full system voltage but rather it sees about 2 volts less. Additionally, the current passing through the coil is reduced about .5 amps.

Q: This Ballast Resistor looks very different from regular automotive Ballast Resistors. How is this one constructed and how long will it last?

A: Inside the anodized aluminum heat sink is a silicon encapsulated resistor. This resistor is constructed of a ceramic core around which is wrapped a length of high resistance ribbon wire of exactly 1.5 ohms resistance. The device is Mil Spec rated at 50 Watts (with sufficient additional heat sinks) but in this particular application will only see about 3 Watts. With such a conservative load, the resistor should give many years of reliable service.

Front View Back View Top View

Q: What can I expect to see different with my ignition system if I instalI a Ballast Resistor?

A: The only difference you should notice is that the coil will not get as hot as it did previously and have a longer life. It will still most likely be hot to the touch however. Maximum temperature should be about 165F. Engine operation should remain unaffected.

Q: Why can't I just install an automotive Ballast Resistor from an auto parts store?

A: You can but it will probably not hold up as well in a marine environment as the Indigo Ballast Resistor. Additionally, most automotive ballast resistors have quick disconnect type connections which are not the most trouble free type of connection for a marine application.

Q: With a Ballast Resistor installed and the voltage reduced to the coil, will the coil make enough of a spark to be able get the engine started?

A: When the starter motor is cranking the engine, the system voltage does indeed drop to about 10 Volts. For this reason, a jumper wire is included with the Ballast Resistor Kit to provide this full 10 Volts directly to the coil when starting. On all late Model A4 starter motor solenoids, there is an #8-32 stud which attaches to an internal auxiliary contact. This stud is normally not energized. However, when the starter motor is engaged and running, full system voltage is present at this stud. A jumper wire can be run from this stud to the (+) terminal on the coil thus providing full system voltage to the coil for starting. Once the starter disengages, the stud is no longer energized. That is OK as the system voltage has returned to its normal level as the starter motor is no longer energized and system voltage is supplied via the normal path.

Q: What if my starter does not have the auxiliary contact for bypassing the Ballast Resistor?

A: The first option would be to try starting the engine without the jumper and see how things go. If you are unable to get it to start, you can wire in a jumper with a manual switch such that the switch is turned on for starting and then turned off for normal operation. If you were to inadvertently leave the switch in the on position, the coil would simply get hotter as though there is not a Ballast Resistor in the circuit.

Q:What happens if the Ballast Resistor fails open?

A: The engine would start but only run while the starter is engaged. It would immediately die once the starter switch was returned to the normal run position. The Ballast Resistor could be removed from the circuit and the engine would operate properly except the coil would run hotter.

Return to Ignition Page
| Home | Ignition | Oil Filter | Fresh Water Cooling | Propeller | Tensioner |