engine not turning over?

if just a click, turn full beam on, fan on,rear heated window and press horn - if sound is weak or tails away then it is deffo the battery has not enough power to turn over engine (9 out of 10 its a battery ) often they seem to have plenty power but they need LOTS to turn a diesel engine. If battery is quite new then alternator may not be charging it. A meter on batt with engine off 12.6v - with engine on - 14v

david
April 2011