Post
Tue Nov 15, 2011 12:15 am
The idiot light of the alternator is an integral part of the charging system, if that is blown the alternator would not charge. At start up when the ignition is switched on the light has a positive on the dash side and receives the negative through the windings of the rotor in the alternator so if it does not come on it it means that either the globe is blown or that there is a break in continuity in the induction system of the alternator. Once the engine is started a positive current from the charging is fed to the lamp, this does not happen as quick as a switch being flipped but rather as the charge is building up from 0 v to full 13v so the light will dim before going out. This is normal but if the light comes on dimly while driving on the open road in top gear with reasonable revs it would indicate a pending failure, usually brushes. A battery that is low in charge can also prolong the dim light and can even cause the belt to screech if not 100% tight.
A bad earth can do all sorts of crazy stuff in our modern cars, remember the engine is controlled by electronics, the sensors read minute voltage differences to adjust the operating parameters and it is quite possible to have the symptoms you described from a bad earth. On my baby I have more than one earth from the battery to the engine and chassis and this helps to prevent funny situations and ensures that the computer can do its work as designed.
If your problem is only at start up I will have a look at the earthing and even if this does not sort it I would not be too concerned about it
Henk Bannink
Some people are wise, some people are otherwise
) but when reading further you mentioned that the alternator was refurbished 
The best explanation I could come up with was that the brushes might be sticky and catching on the housing. Insist that the folks who did the rebuild have a look in to the matter, the symptoms you describe points to brushes not making proper contact and the arcing could damage the slip rings on the rotor.