SnowDrifter

You'd want an ammeter for that. Current's what blows the shit up, not voltage. Impedance is all over the place, can't rely on voltage too tell you what's what have you created an impedance vs. frequency chart?

Oh my What came first? Hot alternator melt the solder? Or solder overspray causing issues? Both?

Retrofit some headlights that have their own power supply. HID or LED You could also look into a DC to DC regulating power supply. Though I'd be pretty loathe to put something like that on a piece of safety equipment as important as headlights

Realistically around 11.7-8v without load if you still want to be able to start your car. Accounting for key on draw, I'd avoid going below 11.4 range. Don't forget to charge your batteries at home doing this. The alternator won't fully juice the things up after a deep discharge

Hey HEY Don't you go talking smack about transpo! As to the codes: Clear them. Nothing much of significance there given the charge issues. All the computers are going to be throwing a fit due to low and high voltage. I'd expect to see the alternator related codes due to your conversion And keep an eye on the steering angle sensor one. Difficult to tell at this point if it's erroneous or not due to the charge issues you've been having

It might be worth your time to re wire your vehicle as far as the big 3 goes. Run dedicated grounds if you need to. And convert the alt to external regulator to use one of the transpo units. Get a clean slate

FWIW I ran 14v batts at 16.1-16.2v on my subaru successfully for a couple years without any stepdowns or other shenanigans. Daily charge should be 2.3-2.4v per cell in temperate weather. Little higher if it's cold as hell. Little lower if you're in triple digits. I know folks go nuts and run higher into the 2.5-2.6v per cell range. Not going to get into that bit. But as a personal preference, I wouldn't want to charge at 14.9 on the daily. For a 12v battery that would be 13.8-14.4v 14v: 16.1-18.8v 16v: 18.4-19.2v

Thing 1. Cool air. You can run ducting to your alt if needed w/ some forced induction Thing 2. More air. RPM is your friend. Alternators have an internal fan. The faster they spin the more air it pulls through. Don't keep the thing under load at low RPM. Rev it up to 2500-3k and let 'er breathe

What are your alternator temperatures? You might need to look into some sort of cooling solution for it. The thing's going to be working fairly hard. 240a on 9k is doable if you're not looking for constant play time, but heat will be you enemy here. A cool alternator is a happy alternator

SMD OM-1

First step is check all fuses Second is disconnect all batteries for 20 to 30 minutes. Reset everything Third is to get a hold of a 2 way scan tool. Start running some self diagnostic checks on your various control modules and go from there. I'd be surprised if you fried anything TBH. Electronics in cars are fairly robust and will generally go into safe mode or turn off if fed power outside of their operational capacity.

Dude chill. Your 'tude is hotter than an alternator at 18v