My 82 Mainship MKI has its original OEM Onan MDJA 3KW genset. It starts and runs fine. The boat has 3 FLA batteries on a NOCO Gen3 charger. The batteries normally show 13.4-14V with the battery charger on, and the main panel shows 120V on either shorepower or generator power. I periodically exercise the generator under medium load for 30 minutes.
I ran the usual generator exercise routine about 10 days ago, with the reverse cycle a/c and battery charger on. I noticed battery voltage measured at the helm dropped to about 12.8V and the voltmeter on the main panel dropped to about 108V. I checked the ammeter on the generator and it was showing -2 Amp.
I started the generator again yesterday and with no load it showed 0 Amp output. I turned the a/c on, and the output immediately dropped to -2 Amp. I shut the gen down and aborted the exercise routine. I switched back to shorepower and everything returned to normal.
I have very little experience with electricity, and have only a digital multimeter. I don't know how to safely begin troubleshooting the issue. Any and all guidance will be greatly appreciated.
I ran the usual generator exercise routine about 10 days ago, with the reverse cycle a/c and battery charger on. I noticed battery voltage measured at the helm dropped to about 12.8V and the voltmeter on the main panel dropped to about 108V. I checked the ammeter on the generator and it was showing -2 Amp.
I started the generator again yesterday and with no load it showed 0 Amp output. I turned the a/c on, and the output immediately dropped to -2 Amp. I shut the gen down and aborted the exercise routine. I switched back to shorepower and everything returned to normal.
I have very little experience with electricity, and have only a digital multimeter. I don't know how to safely begin troubleshooting the issue. Any and all guidance will be greatly appreciated.