Alternator Charging Voltage gradually drops Tried Everything

[DeeZX]

Hi Fellow NICOclub Members,

Maybe you guys can help me with this issue I'm having.

I've added a few electrical components to my 1990 300ZX Twin Turbo i.e. Electric Cooling Fan, aftermarket gauges, and a moderate sound system. I plan on adding a Electric Water Pump, and an Electric Power steering Pump. BEFORE I add these items I noticed a charging issue but it was a small issue so I ignored it.

But when I added the first electrical component, (E-Fan), the issue got worse. When the engine is cold, the charging volts are normal, around 13.9v at idle. when the car heats up the charging voltage slowly decreases. Sometimes when I go over bumps or drive through a puddle, the voltage fluctuates up and down. (weird.. I know). When I take the negative teminal off the battery, the engine sputters to a stop. I Thought it was a slipping belt, then a bad battery, and alternator, Changed all and the problem still exists.

Do you guys have any Idea what it could be? Maybe a bad harmonic balancer on the crank underdrive pulley causing the belt to slip, a bad water pump, (it wines like a supercharger when the engine is cold), with an off center pulley causing the belt to slip, bad ground. Or do you think I need to upgrade the wire to 1/0 AWG-which I intend to do before I install the new MechMan 220 amp H.O. alternator I plan on purchasing? I really want to find out the whats causing this be for I invest in a third alternator.

Thanks!

[Jiinx]

Sounds like you are losing your ground to either your engine or your chasis.

Be careful when taking a battery lead off when your car is running. If you have a voltage regulator that overcharges you could blow every electronic component you have with the voltage spike.

I would find out where your grounds are located and run a good set of larger ground wires, but don't go too nuts on the size! An old pair of jumper cables that had very flexible cables worked for me when I cut them up and used them with another vehicle I had.
Make sure you crimp AND solder the connectors to the cable (whatever one you get) not just crimp. Crimps have a nasty habit of corroding, especially in northern areas.

[NORCAL300ZX916]

^definately ground it should be right above the negative terminal to the frame. u might want to sand off the paint and go to a 1/0 gauge wire or larger since u have all the additional electric accesssories. also to be sure its a ground check the voltage at the alternator if its fluctating at the alternator u may have purchased an alternator with a bad voltage regulator which is common for discount parts store parts.

[evildky]

the main ground wire hooks both to the firewall and to the trans/engine at the bellhousing

when you disconnect the battery while the car is running, what kind of volts is your alternator putting out? even with all the extra load you shoudl have 14 volts ro there abouts, do you have an underdrive pulley? this slows down the alternator and ti might not be getting excited (not pervy thats just what it's called )

and if you do put a big fatty alt on you will need to upgrade the wiring