Edd, Do you have an internal or external voltage regulator (charge controller). Regardless the alternator is probably putting out the amount of voltage required by the regulator. Often times the voltage being supplied by the alternator is different than that being sensed by the regulator. Recently one of the listers had his sensing line corroded to the point of falling off. In this case regulator sensed too low of a battery voltage and drove the corresponding alternator output up...to ~33v! Likewise if high resistance on the output cabling or voltage being dropped across a battery isolator diode is causing the regulator to think there is more voltage being sent to the batteries than there actually is then the regulator would drive alternator oupltput down. The voltage drop across an isolation diode is about 0.7v and the normal full charge voltage for a standard wet lead acid battery is 14.4v. So 13.7v is easily explained. If the contacts or cabling are getting old and corroded then the remaining 0.5v drop to 13.2v is explained. The cabling included the ground connections made by mounting the alternator to the engine and the bonding/ground cable feom the engine to the batteries.
Check and compare the voltage at the alternator output terminals, the battery terminals, and the sensing terminals. Yes a loose belt can cause low output but you would probably hear it. Once it stops slipping the output returns to normal. Good luck, Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons ,MD On Jul 31, 2014 2:13 PM, "Edd Schillay via CnC-List" <[email protected]> wrote: > Listers, > > Lately, when the engine running, I'm seeing the voltage reach 13.2 tops > when it used to be much higher (13.7 to 14.0). > > Is this an alternator issue or is it the belt tightness? Any suggestions > would be much appreciated. > > > All the best, > > Edd > > > Edd M. Schillay > Starship Enterprise > C&C 37+ | Sail No: NCC-1701-B > City Island, NY > Starship Enterprise's Captain's Log <http://enterpriseb.blogspot.com/> > > > _______________________________________________ > This List is provided by the C&C Photo Album > > Email address: > [email protected] > To change your list preferences, including unsubscribing -- go bottom of > page at: > http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com > > >
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