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Bouncing alternator ammeter1. Resistance in regulator sense circuit. Piper Cherokees that use the round ammeter are prone to this type of problem.The regulator circuit senses through the bus bar, thru the circuit breaker and thru the master switch. Resistance in the circuit and the fact that the sense is late in the circuit electrically results in poor power regulation. Some airplanes use regulators with a remote sense that sense voltage directly from the alternator. Clean or replace the circuit breaker and master switch contacts. It's possible to rewire the circuit so the regulator senses more directly what the alternator is doing but such a modification would require FAA approval.
2. Cessna single engine 12 volt systems. When using the Electrosystems VR600A regulator a poor electrical connection anywhere in the circuit from Pin S to the system bus can result in unstable voltage regulation, a wildly fluctuating ammeter, and flickering panel lights. Electrosystems manufactured the VR600A, a combined voltage regulator and OverVoltage sensor. The VR600A is not compatible with the standard Cessna wiring system. The VR600A installation instructions require a substantial wiring change. The OV Sensor is removed, the master switch is bypassed in favor of a pull type circuit breaker, and the power in and voltage sense are moved from Pin A to Pin S of the voltage regulator. The solution is returning the wiring to its original configuration and replacing the VR600A with the R15V00 Rev A regulator from Zeftronics. 3. Dirty electrical contacts causing a build-up in resistance in the field circuit between buss and regulator : feedback from some of our readers: Problem: Grumman AA1A load meter fluctuations. T/S manual recommended cleaning slip rings; while cleaning, alternator bearings fell out. Replaced with rebuilt alternator, problem continued. Verified grounds, went to replace voltage regulator; prior to replacement the installation manual noted fluctuations often result from continuity problems. Sprayed alternator circuit breaker & connections liberally with ACF-50. Problem went away & stayed away. Have new alternator & spare regulator; 30+ years experience, A&P/IA but never too old to learn! After 3.5 years and several regulators, one alternator and one master switch later. The problem with the jittery ammeter was found to be a weak connection in the aircraft voltage regulator connector. Cleaned and tightened. Now it\'s so steady it\'s not very exciting to watch anymore. Bob Nuckolls article (in Adobe Acrobat format) When a Good Ground
Not? at http://www.aeroelectric.com/articles/grnding.pdf
at the end of the article has an excellent technical description of the problem.
(thankyou Bob)
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