jdb7566 Report post Posted May 4, 2014 1999 Monaco Diplomat 38A, tachometer quit working, alternator light is on, gauge shows charge rate of 12v. Engine batteries are less than 1 year old, and are fully charged. Any ideas on where to look before I take to a repair facility. Thanks for your help. Share this post Link to post Share on other sites
wolfe10 Report post Posted May 4, 2014 On many coaches, the alternator also provides the tach signal, so it is quite likely the two are related. The problem could the be the alternator, regulator or a battery isolator. Could even be that a wire came loose. It could also be the belt, but were the belt to break on all engines but the Caterpillar 3126, the engine would overheat. Any shop that works on alternators can diagnose this. Share this post Link to post Share on other sites
dickandlois Report post Posted May 4, 2014 OEM alternator, could mean the brush's are bad. Check for alternator exciton voltage at alternator when ignition key is in start position, have a tech check it if you are a person who works on your own equipment. Voltage output for an alternator is between 13.5 to 14.5 volts, when the batteries are at or near full charge. Like Brett mentioned, belt issues! Might be time for a new or rebuilt alternator. Rich. Share this post Link to post Share on other sites
