Volvo md2020 alternator

[Monte147]

I am noticing low charging output when cruising, voltage just 13.2 and battery monitor showing a mere 9amp. Doesn't this seem low? Thanks

[Pete7]

Yes, that's rubbish. First off, are the batteries full so they won't accept any more?

Have you checked all the connections are scrupulously clean including earth returns?

Pete

[Monte147]

Batteries running low as am out at sea, hence I noticed cause in need of some juice!
Connections look good. Measured with multimeter the output under 2500rpm, just 13.3v. In the past used to reach 14v and even beyond. Could be alternator nearing it's life...

[Pete7]

Hmm tricky, because an inspection would mean taking every connection apart, cleaning it and re-assembling which you are not going to do at sea.

Were are you taking the 13.3v reading from? back of the alternator?

Alternator could be getting tired, its probably 3 decades old now and was originally just a cheap car alternator. When you have the chance, swop it out for an OEM one. Did ours a couple of years ago for £160 and included an upgrade to 100A from 50A. You will need washers to align the belt properly, so keep the old ones.

How old are the batteries btw?

Pete

[Monte147]

Yes will give it some work while in marina. Thanks

[Pete7]

Pay particular attention to the earth if it goes to the engine block. Volvo were a bit mean with the size of the wire and 3 decades of corrosion did the rest for us.

Replaced with a wire straight to the batteries from the alternator. However, we have a propshaft so don't worry about galvanic corrosion or the need to isolate the alternator on some Volvos.

Pete