my old alternator had this device between 2 terminals on the backside.
any one know what it is? or if it is needed? i have a two wire external voltage regulator.
thanks for any and all replys.
my original problem was an overvoltage of 16 volts on the engine monitor.
i found alternator bearings very noisy. and this diode separated,nonfunctioing.
rebuilt alternator is ordered. and if i can obtain a new diode like this one. hoping that will fix my overvoltage.
i have replaced the cessna master switch, (no change). and checked numerous conections,(no change). and tightened the loose alternator belt, (no change).and replaced the 2 wire external voltage regulator,(no change).
i plan to replace the field switch at the panel next. as i suspect the new alternator and new diode will not cure the overvoltage.
any other checks recomended?
I can't see the part number, but my guess is that it is zener diode installed as part of an overvoltage clamp. Clearly, it has been 'tripped' and is no longer functioning.
Neverless, if it it an OVP clamp, it may be the wrong place. Time to find a local guy with the nickname 'Sparky' or similar to help you work through this one.
If you can post the part number, I can confirm my hypothesis.
With sufficient applied voltage and current, they become what we like to call an NED -- "Noise Emitting Diode". It emits a loud "SNAP!" noise.Zeners don't "trip" like a fuse; the reverse biased junction breaks down a certain design voltage (there is a wide range .. device dependent), and does not cause damage unless the reverse current is over the design limit (the damage due to heating). When operating normally, it acts as a poor man's voltage regulator, not allowing the terminal voltage to rise above the zener voltage.
Does it have any evidence of burning or blistering? I can't tell in the photo. One thing to consider is that it failed due to vibration stresses...