Joe, #1.Have you cleaned all your battery and battery ground connections. #2. Did you tighten the b+ bolt on the back of the alternator. That's where all the brown wires come together, If it's not clean and tight then you will get a low volt reading. #3. The main relay may need the contacts burnished / cleaned. The power for the fans when using the Fan Zilla comes thru this relay. I'm not an expert on the Fan Zilla, but as I understand it, it just staggers the fans coming on but does nothing to lessen the load on the system. Thus you will still have a low volt reading on the alternator. #4. What alternators have you been using. If your swaping out the motorola and ducy and they ar all used, then you may be going from bad to bad. #5. Is the circut breaker for the fans getting hot. If so you may have a fan motor going out and it's drawing more current than the system can handle. Both fans warm and running will draw about 28 to 30 amps dc. #6. What about your battery, Is it fully charged. An alternator can't do it's job without a fully charged battery. This is all I can think of for now, and if problem persist then it may be The Fan Fix and De Lorean 140 alternator time. John