240z alternator upgrade (instructions w/ pictures)

[Jarvo2]

So while digging through my box of parts that the previous owner provided me, I ran across a brand new alternator, which ended up being a 280ZX internally regulated 60amp model. After upgrading to the Pertronix electronic ignition last year, I began to hear that the 240z's voltage regulator and 40amp alternator might not be powerful enough, so I investigated upgrading. All it cost me was the price of a diode ($2 @ Radioshack) as I had all of the other parts already.

After removing the voltage regulator I found out why its recommended to go with an internally regulated alternator -- look at how the backing plate has melted!

In order to eliminate the external voltage regulator I needed to create a jumper, including a diode to allow the car to turn off when the key is removed. Here is the best diagram I was able to find on the internet (thanks to the user who posted it here first!):

I ended up using a spare voltage regulator connector (and kept the somewhat working voltage regulator in one piece in case I ever needed to switch back). This connector then plugs in just like the voltage regulator would.

Once installed with the waterproof boot that I had laying around (which fit perfectly), I was able to tuck the jumper harness under the wires and it looks like its always been there.

Now that I've been driving on the new alternator without the external voltage regulator I can honestly say the car is running better than it probably did when it was new. This was a great upgrade and should be done by anyone having ignition or performance issues (I thought it was my carburetors, but all along it was electrical issues).

[EuroDat]

Good write up Dave. It would be a good addition to the Technical Articles.

Chas

[Jarvo2]

Thanks. Dave Irwin just pointed out that this is only valid for 70-72 240z's as the 73 with an OEM electric fuel pump needs to be rewired to prevent battery drain.

[240260280z]

Excellent!

[Carl Beck]

Of course - Dave Irwin was selling the plugs pre-make, to anyone that wanted one - years ago here.

FWIW,

Carl B.

[Mikes Z car]

Terrific writeup. Great pictures too.

Is the 280ZX alternator the best to use to switch to an internal regulator or is there another more widely used alternator (possibly a cheaper GM or whatever) that will work? I have read going with a GM alternator requires a bracket modification.

Mike

[Nobsz]

Hi, I have done your swap in my 1973 240z. the swap worked, however my 12v yellow wire on the harness is melting??? What would cause this? Is it the starter wires? could it be multiple problems? how much money to take it to a shop if i dont get answers here? thanks for any input

[SteveJ]

Of course - Dave Irwin was selling the plugs pre-make, to anyone that wanted one - years ago here.

FWIW,

Carl B.

They are available through MSA: Motorsport! Alternator Upgrade Adaptor, 70-73 240Z - The Z Store! Nissan-Datsun 240Z-260Z-280Z-280ZX-300ZX(Z31/Z32)-350Z-370Z Parts.

[SteveJ]

Hi, I have done your swap in my 1973 240z. the swap worked, however my 12v yellow wire on the harness is melting??? What would cause this? Is it the starter wires? could it be multiple problems? how much money to take it to a shop if i dont get answers here? thanks for any input

The wire is melting due to too much current. With no pictures, meter readings etc., it is difficult to diagnose the problem. It would not be due to the wires going from the battery to the starter. What is your ammeter reading when you're driving the car? How old is the battery?

Maybe you should try the plug that MSA offers: Motorsport! Alternator Upgrade Adaptor, 70-73 240Z - The Z Store! Nissan-Datsun 240Z-260Z-280Z-280ZX-300ZX(Z31/Z32)-350Z-370Z Parts (Gee, this link looks familiar. )

[Nobsz]

The wire is melting due to too much current. With no pictures, meter readings etc., it is difficult to diagnose the problem. It would not be due to the wires going from the battery to the starter. What is your ammeter reading when you're driving the car? How old is the battery?

Maybe you should try the plug that MSA offers: Motorsport! Alternator Upgrade Adaptor, 70-73 240Z - The Z Store! Nissan-Datsun 240Z-260Z-280Z-280ZX-300ZX(Z31/Z32)-350Z-370Z Parts (Gee, this link looks familiar. )

Yes, but we all learn the hard way. After a few hours of research, i found if i connect 1-5 and 2-3 on the connector, then i had 12 volts at the 2-3 connection... and that is where i put a diode. i found that the 5-6 connection doesnt work for 1973's, and the correct way is 1-5. however, when i connected this way, my voltage needle was on the middle line inside my cars' ampgauge. i dont think im getting the battery charging from the alternator.

[SteveJ]

Did you point the Diode the right way? If not, the alternator won't see the battery voltage.

[Nobsz]

Did you point the Diode the right way? If not, the alternator won't see the battery voltage.

-yes, the silver line is facing the number 1 pin.

(update) i disconnected the jumper plug and the voltage regulator. the car runs fine. what is going on? :stupid: i think the car has been rewired.

Edited July 17, 2013 by Nobsz