91 JETTA 1.8L – 2x Alternators = No Voltage

Charging issues on my 91 Jetta. For The last week I’ve been trying to fix my charging system with no luck. Started off with the car dying due to the battery being drained down but the low battery light on the dash never came on (???). Checked voltage at the battery and it’s below 12v so the car is running only on the battery. Checked the outputs at the alternator only picked up the battery…no 14v in DC and no AC in case reg died. Did a continuity and resistance check of charging cables they’re good. Cleaned connections and terminals including blue cable on alternator. Nothing. I have the valeo style unit so I managed to find a new set of brushes…installed still no output at unit. A friend had a rebuilt bosch unit that he lent me to try and that too doesn’t put out any voltage. Any ideas?