Alternator charging low

[andreas.mehlin]

Volvo penta md2020
60amp alternator

Often only charge 3-5amp. When turning on watermaker it changes more because My bat meter tells me about the same balance. So it seems to charge good or at least kick in more amps when more load is given

Ok or not ok?

[hlev00]

Just to be sure, is the state of charge of the batteries low enough to accept a higher current?
How are you measuring the charging current?
If the alternator is delivering more current when more demanded, it seems to be a problem in the path or perhaps the battery.
How old are the batteries? Has this deteriorated over time, or suddenly changed?
Check for bad connections in the path from the alternator to the batteries. You can use a multimeter to measure the voltage drop across the positive path then the negative path with the engine on. It should be less that 0.5V. Higher than that indicates some resistance in the path. With the engine off the same paths should show near 0 Ohms resistance.

I've found Charlie Wing's book pretty good for explaining and helping think through troubleshooting process.