Originally Posted by
foama
This thread seems to be going in circles. Let me sum up as I understand, maybe something productive comes out of it.
You replaced the alternator and battery because it wasn't charging, and thats when problems started. The regulators in these alternators are a bit different than most. They have one connector that goes to the main ECU. The ECU has the ability to charge the battery regardless of charging state (simple form of regenerating energy) when you take your foot off the gas at revs higher than about 1800rpm. If something was F***ed up connecting the alternator, maybe the ECU got fried. Quite improbable, but none the less possible.
Have a good look at the interior fuse box and its connectors. It is to the left and underneath the steering wheel. Are all connectors and fuses and other parts snuggly in? Check by pushing each of them, do not forget any.
In winter kick-panel harnesses are of special interest! Go get a strong magnifying glass and a good light source. Remove each connector and take a very good look at where each individual wire meets its connector pin, and look at it, each single one, individually one by one! On the jack side and the connector side! Every darn single wire! If it has the slightest signs of corrosion or become greenish, where wire and connector-pin meet, there is one very likely and major source of fault!
Blind spraying with contact spray is a just placebo at best. You need to do this job and the next below very thoroughly and with enduring patience.
Engine side wire harness. As Fummins said, have a very good look at each single wire. Even if it just looks good, it doesn't have to be OK. Lightly pull each wire to check if it may be broken inside. Sometimes they break inside and the outside looks like new, with the insulation simply covering an internal break. Does the light show go off when you wiggle or kneed that harness? Check!
The fuses under the red plus-pole cover, are they in order? Check!
The outside fuse box near the battery, does it look good inside?
I can only guess from here, but I would check what is easily and quickly done first, then investigate what takes more time.
I understand its freezing cold outside, but don't rush things because of that. Do one thing after another, go inside and warm up if needed, but do what you must do very thoroughly.
Good luck!