Good technicians are LAZY technicians. I just got through sending the company a double-digit IQ grade, list of questions. I don't even wanna pop the hood and trace down the wire to the ECU. But before anyone grabs a 24" Stihl and goes to work allow the company to respond. Won't cost a nickel.
Case grounding is common on both A and B field circuit external regulators. For years I SOLDERED a wire with a 1/4" ring terminal atop a reg mounting hole. Both in the 540-series of Ford external regs and the 8312 series of MoPar external regs.
One of the two wires on the MoPar alternator is IGNITION SWITCHED POSITIVE. The other wire goes to the ECU. Disconnect one wire and use a test light to verify which is which. Key on but engine off. Remember this terminal.
Prepare to voltage probe this wire while it is connected charging with every accessory in the car switched ON. Drain the battery a little before starting the engine. Start the engine using a volt drop check. Meter positive probe on the alt output stud the neg probe on the field wire connection I told you not to forget.
Half a volt drop is too much. Fix it even if you have to do it using a Bosch type relay. Low voltage is low field current which is low alternator output. Total all-out ampere potential. If voltage drop is seen fix it.
