Merc. 309D Alternator Dash Light

Charging light remains on in cab regardless of engine rpm. Have done voltmeter test across battery and seems to be functioning properly. (12.7V not running moving to 14.5V at 3000 rpm) Anything obvious to look at with these vans, or should I assume alternator giving up?

Don't assume the alternator is giving up.
By the sound of your voltage readings,the charging system is working ok.
More likely that the wire to the light is earthing out somewhere - i.e. insulation rubbed through and touching metal.

Thanks Power Tool, our opinion of the charging system concurs. The RAC however disagree and have told the owner that he needs a new alternator. And this is after sorting him out with a new battery on first call out. Obviously not charging after fitting as he called them out again 2 days later to have them drop him at a garage to purchase a new starter motor. I suspect the problem was a few bad connections and he could have saved a few quid - have cleaned them up and as mentioned charging seems ok. Have to sort the dash light though - cheers