Originally Posted by CJ7-Tim
PCM failure is very highly unlike. Poor quality or loose wire connections, and/or old corroded wires will result in poor charging. Did you test the alternator ? Just because the alternator is new, doesn't mean that it works right
It's got a lot to do with why I don't deal with chain stores - I used to work for one, and I'm familiar with their parts and testing procedures (both at the factory and in-store.)
Disconnect negative cable from battery.
Check all of your mains connections - clean/reterminate PRN.
Check the wiring on the back of the alternator - clean/reterminate PRN.
Check the studs on the back of the alternator - clean PRN.
Check the mounting for the alternator, as it is also the primary ground for the unit - clean PRN.
Inspect the fusible link wire in the alternator output lead at the PDC - replace PRN (if the insulation is blistered and it feels like there isn't a wire in there - there isn't. Replace with 10AWG fusible link wire, or with a fuse format that gives you a 125-150A rating - I believe your 1999 will have a 117A alternator, OEM. It's a fuse, it's there for a REASON.)
Inspect, clean, reterminate positive mains leads PRN.
I know I said to start with the grounds - that's because, in thirty-odd years of working on cars, the amount of electrical issues I've traced to shonky grounds has run up around 85-90% of them. It's as good a place as any to start, and offers the following advantages:
- It's cheap.
- It's easy.
- It probably wants doing anyhow.
- It will get you in the neighbourhood of other components that may want checking, and therefore get your eye on them.