The following information is derived from the FAA's Service Difficulty Reports and Aviation Maintenance Alerts.


Beech C33A Debonair

Shorted Voltage Regulator

Overvoltage warning light illuminated. Installed a new voltage regulator (p/n R1530b), started engine, switched on electrical system, warning light came on. After troubleshooting with manufacturer’s support, unit shorted internally. Manufacturer blamed faulty alternator and would not honor warranty. Unit will not work with this system no matter what manufacturer advertises.

Part total time: 0.0 hours

Beech A100 King Air

Improper Test Procedure

When the aircraft is equipped with VR-1010-24-1a voltage regulators as allowed by manufacturer Service Instruction 0766-354, rev II, the overvoltage testing procedure is not achievable. The solid-state voltage regulators are not adjustable to a range that will adequately test the overvoltage relays, more than 31.5v. During a ground run and adjustment of the voltage regulators, one regulator failed and caused an overvoltage condition. It is this tech’s opinion that the test procedure for the solid-state relay should be changed to include removing and bench-testing voltage regulators.

Part total time: n/a

de Havilland Canada DHC-2

Overheated Resistor

Immediately after departing, a strong burning odor was noticed in the aircraft. The aircraft returned to its base, where maintenance determined that a resistor within the voltage regulator (p/n 15891F) overheated and was the cause of the odor.

Part total time: Unknown

Gulfstream 690

Failed Voltage Regulator

Aircraft voltage on #2 engine was above 30 volts, kicking either the left or the right generator offline. The #2 voltage regulator (p/n 104217A) was replaced, balanced and ground function checked okay.

Part total time: Unknown

Learjet 35A

Burned Voltage Regulator

Right generator light illuminated during final approach. Detected odor of smoke. Found the volt regulator burned.

Part total time: 11,311.0 hours

Piper PA-31-350 Navajo

Shorted Left Alternator

The pilot reported the left alternator amps went to zero and the right alternator warning illuminated. The right alternator was reset, went to 70 amps and failed again. Then the left alternator went offline. The right alternator was successfully reset, but the left one remained offline. The pilot declared an emergency, returned and landed without incident. Troubleshooting determined the left voltage regulator (p/n B-00286-1) was the problem.

Part total time: Unknown


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