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Ammeter failure?


Cloudmirth

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What is it with Mooney ammeters?  My first Mooney was a ‘69 M20C which was one year old when I bought it.  The ammeter never really worked barely showing a reading positive or negative regardless of load.  Never solved the problem in 5 years of ownership.  Move forward 45 some odd years and I have another ‘69 M20C (go figure) and the ammeter barely registers.  The battery stays charged and a voltmeter reads 14 volts when the alternator is operating.  Ignoring the ammeter worked back in 1975 but I’m older (if not wiser) now.  It seems odd that two planes separated by 45 years would manifest exactly the same problem.  Any thoughts?

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The ammeter will only show positive or negative if the battery is charging or discharging, and as long as the alternator is capable of covering the load at that rpm, you won’t see a change of the ammeter.  Typically with a good battery, you’ll see a slight charge after you fire up the engine and neutral for the remainder. A load meter is a different story and will change with adding load. 

 

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