I have a 98 748sps owned from new. Mine has a 2phase 350w alternator. These were renowned for being on the limit for charging when the lights were on. If the charging circuit(wires and plugs) weren't in tip top condition then the battery wouldn't get sufficient charge. The lights were/are poor. Some folks wanted the dip to stay on when main beam was on but soon found the battery going flat. The 3phase alternator is 480 or520w and was better but still considered a bit weak again if the charging circuit isn't in pristine condition. Ive got much heavier guage wires from the alternator with no plugs straight to the reg/rec They can
Did the same tests across both bikes , monster 900 1997 and the 748s , negative battery as reference, engine idling , lights on and off Similar results, discrepancies, across the battery, pin 30 and at fuse 15 with lights on/off Monster will have the 350w alternator and the 520w in 2002 748s , 748s is marginally better across the tests
I would start by connecting wire from battery to fuse out check voltage if the same, connect to fuse in, if the same this rules out lighting fuses/fuse connectors, connect to relay out (30), if the same connect to relay in (87), if it’s the same connect to fuse 1 try both sides From diagram all power to this cct is via fuse 1 (from battery) then relay 87 to relay 30 to lightning fuse For this sort of job I use https://shop.snapon.com/product/Dig...ay-Circuit-Tester-(4-49-V-DC-Range)/EECT424HD Other (far less expensive) makes are available As then there is no need to muck about with wires from the battery
Thanks for the help , good skill to have Spent a few hours tackling it , got it sorted , stripped , depinned , cleaned , dielectric grease , redid the loom sleeve , hopefully keep the back if the fuse box clean
