ideally, most alternators charge at about 14.5v. yours is probably just about acceptable at 13.5v, but you should check it under load, by switching on high drain items, ( with the engine running ) such as the headlamps & blower motor at full speed. leave them on for several minutes & watch the volt meter, it should stay pretty much stable. if it falls any lower then it may have a problem. check all the connections to battery & alternator & check those that you havn't had off, such as the main earth cable to the engine.
jim, January 2010
