Battery charging warning light

[Swanrad2]

Hi,

The offending light on the instrument panel of our Volvo MD11c started coming on and staying on a while ago. We hadn't used the batteries much for 3 years but kept them trickle charged before launching. Has anyone got a diagnostic procedure we could follow to see what is going on?

Something like:
1. Test battery condition using ....
2. Test alternator output using a ..... Which should be in the range of .....

Etc

Thanks

 

[VicS]

I would test the battery volts after it has rested with no charge or load for 12 hours or so. For good well charged battery I' d expect at least 12.6 volts. Preferably 12.7 to 12.8

If it has removable filler caps testing with a hydrometer is better as you get a separate indication for each cell.


With the voltmeter connected start the engine and watch the volts. After a drop when cranking they should quickly recover then rise slowly to 14 to perhaps 14.4

However check all the connections in the panel and on the alternator.

If it is NOT the original 35amp alternator the brushes or slip ring could be worn or dirty . An original 35 amp alternator will mostly be a type without brushes.

Getting the alternator tested by an auto-electrician could be a wise move. If defective they should be able to repair it quickly and economically.