240Z Alternator Upgrade

Datsun 240Z Alternator Upgrade

Consider replacing your old stock alternator and external (mechanical) voltage regulator with a newer, higher capacity, solid-state internal voltage regulator alternator.  The alternator upgrade is easy, with a couple of options for the wiring.

I had my old, stock alternator finally shot craps at 80 mph in the fast lane of a Southern California freeway.  For whatever reason (H4 headlights?  400 Watt amplifier?  Seat heaters?) it went to a dead-short to ground, blew the fusible link, and that’s all she wrote.

For reference, here is the stock alternator that uses the external mechanical voltage regulator. FWIW, I kept the old voltage regulator in place, and just tucked the wiring into the main harness, so it looks like it’s still ‘in the circuit’.

240Z Alternator Upgrade - original alternator

Original alternator.

I had the ‘New’ alternator tested (O’Reilly Auto Parts) before I took the time to bead blast the casing. Unfortunately, I no longer have a record of the manufacturer or model number.

240Z Alternator Upgrade - Both Alternators Rear View

‘New’ and old alternators

Here are three wiring diagrams.  First is the stock wiring, with the mechanical voltage regulator for reference.  Second is the approach that uses a jumper in place of the mechanical voltage regulator.  Third is what I did, a modification to the wiring harness.

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Images below show the placement of the diode in the “L” circuit.  Some references claim the care will keep running if this diode is not in place.  Figured better safe-than-sorry.  Since the environment in an engine compartment is so ugly, I opted to crimp-and-solder both ends of the diode into the cable.  Notice the white stripe on one end of the diode.  It is important this is on the side of the diode facing the alternator.

240Z Alternator Upgrade - Detail showing diode in shrink tubing

Detail showing diode in shrink tubing

240Z Alternator Upgrade - Detail showing diode attachment into wiring harness

Detail showing diode attachment into wiring harness

Below shows the details of the different colors connected to each other as well as the diode

240Z Alternator Upgrade - A close-up view of the modified "S" and "L" connector

A close-up view of the modified “S” and “L” connector

Here is the wiring just before closing-up into the wiring loom.  The “S” and “L” wires are inside anot

240Z Alternator Upgrade - The solder-and-shrink-tubing before re-installation back into the wiring loom

The solder-and-shrink-tubing before re-installation back into the wiring loom

Here is the final shot of the completed install.  The old mechanical voltage regulator is still in place to maintain a more ‘stock look’, although the wiring is not connected at all, just tucked into the wiring loom.

240Z Alternator Upgrade - Finished wiring loom to alternator

Finished wiring loom to alternator

Wire Loom Cover

I knew I would be in-and-out of my wire harness, so I wanted a sleeving that would be durable, good looking (not that black plastic corrugated crap) and chemical/heat resistant.  I found an excellent solution at McMaster Carr with their Easy-Open Polyester Wrap-Around Sleeving Braided.  I ordered:

  • 25ft 1459T22, 1/4″ ID, 3/16″ to 1/4″ Bundle Dia
  • 25ft 1459T23, 1/2″ ID, 5/16″ to 1/2″ Bundle Dia
  • 25ft 1459T24, 3/4″ ID, 9/16″ to 3/4″ Bundle Dia

References

AtlanticZ.caAlternator Swap (Putting an ’82 280ZX alternator in a ’77 280Z)
zcarcreations.com: HowTo Voltage Regulator
Capital Z of Texas:  Datsun Z Alternator Upgrade to GM CS130 Alternator
Datsun Z GaragePERFORMANCE MODS and ENHANCEMENTS (scroll down to “SEVENTH- Ignition”)

Related cool photo

When the old alternator crapped-out, I had to get a tow.  I got this cool photo of the shadow of my 240Z on the flat-bed tow truck when we stopped at a light.

Shadow of my 240Z on the flat-bed tow truck

Shadow of my 240Z on the flat-bed tow truck

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