Diodes To Protect The Electrical System and Why

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Originally Posted on Sat Jul 23, 2005 10:28 am

Diodes are magic things, used to protect the sensitive electronics on planes from the relatively large "kickback" pulses due to the collapse of the magnetic fields of the battery solenoid (and starter solenoid for those with switch start) and the starter and regulator and controlling switches. The are rightfully called "snubbers" because they snub the reverse kickback from several hundred volts to less than one volt.

The need is explained in an article by a true expert who made actual, finite measurements of the reverse pulses with and without the diodes.

This article tells why the diodes are needed, how they work, and how to create and install them and what the odor of burned diode means if you don't follow the instructions.

As a benefit, the service letter by Cessna showing and calling out an inexpensive (the only Cessna thing that fits that category) replacement solenoid is also included in the article.

Neal