Alternator problem and... ?

First of all check all the wiring connections to the alternator, particularly the ground connection.

It might not also hurt to reach behind the instrument cluster (I'm thinking of C900's here) and push the two multi-pole connectors into the back of the cluster properly just in case they're loose. That's to see if the connections to the charging lamp are not good since if the lamp blows or becomes disconnected due to wiring elsewhere coming astray, the battery won't charge at all.

If you would like to give the alternator a thorough test there are a few ways - most of us (me included) don't have proper alternator testing gear so have a look at these URL's to get some ideas:

There are no doubt other good references covering alternator and charging system 'debugging'. If anyone knows of more, let us know.

Regards,

Craig.

But why would it start off of a portable jumpstart thinger and not its own battery which reads 12.55V with the key off? That's what mystifies me.

Probably the battery has good voltage but cannot produce suffcient current. I think this is common.

John

If you have a new battery in the car it will read 13.8 volts when fully charged. Replacing the voltage regulator without cleaning the armature, which builds up oxide and carbon over time, may not cure the charging problem. Like the other poster suggested you most likely have poor connections from the plus and minus side of the battery. Try cleaing the ground to frame connection carefully.

Alternator may be grounding the battery positive terminal. I would undo all connections to it and start over.