Might be undersized or weak on your alternatorIJ We have 100 or 110 amp on ours but do not run at night, thinking I would need 150 amp to turn the lights on.. We generally have dew that falls at dusk most nights and we head in on a regular basis.. If the regulator in the alternator is working properly it will provide only what is needed and will not hurt the system. Pull it and have checked to see what its capacity is.. Gleamer
Idealy I would rev macine at least half throttle and turn on all electric load. Check voltage at battery, alternator, starter pos post, both terminals of master breaker, and both terminals of cab master solinoid. This will track how voltage is doing all the way to cab. You can set your digital meter on volts and put one leed on each of the master breaker and master solinoid posts. You would be allowed .2 volts accross these connections. If all is well up and into cab you could hook jumper cable between known good cab ground and frame to see if voltage comes up on gauge. Then you could do the same between good ground in overhead and frame. look for ground stud behind about the third from left tattletale module or covers. There is not a real heavy wire that runs up to tattletales from fuze block to voltmeter and tattletale with low voltage alarm so it can be misleding for what you realy have available for clutches ect. I'd do a few of these tests and then I think a guy can narrow down major part of your problem. Good luck. Oh and I wouldn't trust these rebuilt alternators we get these days for they are alot of the times right off the get go or after very little use.