October 2019 Service and Repair ManualManifoldsPart No. 1280490GT S® -80 XC ™ • S® -85 XC ™ • S®-80 HF • S®-85 HF 79How to Test a Coil DiodeProperly functioning coil diodes protect theelectrical circuit by suppressing voltage spikes.Voltage spikes naturally occur within a functioncircuit following the interruption of electrical currentto a coil. Faulty diodes can fail to protect theelectrical system, resulting in a tripped circuitbreaker or component damage.Electrocution/burn hazard.Contact with electrically chargedcircuits could result in death orserious injury. Remove all rings,watches and other jewelry.1 Test the coil for resistance. Refer to RepairProcedure, How to Test a Coil.2 Connect a 10W resistor to the negativeterminal of a known good 9V DC battery.Connect the other end of the resistor to aterminal on the coil.Resistor 10ΩGenie part number 27287Note: The battery should read 9V DC or more whenmeasured across the terminals.1 multimeter2 9v DC battery3 10Ω resistor4 coilNote: Dotted lines in illustration indicate a reversedconnection as specified in step 6.3 Set a multimeter to read DC current.Note: The multimeter, when set to read DC current,should be capable of reading up to 800 mA.4 Connect the negative lead to the otherterminal on the coil.5 Momentarily connect the positive lead fromthe multimeter to the positive terminal on the9V DC battery. Note and record the currentreading.6 At the battery or coil terminals, reverse theconnections. Note and record the currentreading.Result: Both current readings are greater than0 mA and are different by a minimum of 20%.The coil is good.Result: If one or both of the current readingsare 0 mA, or if the two current readings do notdiffer by a minimum of 20%, the coil and/or itsinternal diode are faulty and the coil should bereplaced.
