If the earth for the dash lights is loose the power can sometimes feed through the bulbs they would normally be slightly dim. It could be a blown component on the dash or a short feeding power in to the dash circuit.

It is possible that the alternator is faulty but still charging, it will not show full voltage at 1200 rpm, you should get nearly 14v on a healthy alternator but if one of the diodes has blown it will not get to 13v