i have a 1990 talbot express 1300 D 2.5 diesel motorhome which does not seem to be charging properly i have had the alternator checked and is working properly the battery is brand new and fully charged when i put a voltmeter across the battery it only reads 12 volts and does not move at all when the engine is started when driving the charging light on the dashboard flickers all the connections have been checked and are tight can anybody help me with this problem please