Wiring up a 280zxt alternator on a 240z

[jtmny1999]

Anyone please help I can't get my alternator to charge the battery on my 240z. This is the way I connected it, there are 3 wires the fat one from the alternator on the bolt goes directly to my battery +. The connector that has a medium and thin one, the medium one goes to bat + the thin one goes where? I tried puttin the thin wire on to positive, but still wont charge. I also tried puttin a bulb (thin) on positive and grounding it the bulb it stays on but wont charge please help. Or is my alternator no good?

 

 

thanks

[zcarnut]

What instructions did you follow?

 

Here is a procedure I came up several years ago:

 

 

Converting a 240Z to an internal regulator alternator

 

Because I don't like to give instructions without some explanation

of what you are doing (it makes troubleshooting easier), I will

start by describing the internally regulated alternator's

electrical connections:

 

An "L" connection which goes to a "switched" 12V supply. By this

I mean a 12V source that is active only when the ignition switch is

in the ON position. I use the mnemonic "L" for "lamp", the

alternator warning lamp (if used) is in series with this

connection. This terminal also supplies the "excitation" current to

the alternator field winding at engine turn on, allowing the

alternator to begin producing voltage as the engine is ramping up

to idle speed. Once the alternator rotor is turning fast enough, it

generates it's own supply for the field winding and the current in

the "L" connection stops flowing. The warning lamp (if used) goes

out.

 

However, if the L connection is connected directly to 12V supply,

when you attempt to turn the engine off, the alternator will supply

power to the switched 12V loads and the engine will continuing to run

even you turn the key to the OFF position!

 

To prevent this from occurring an electronic component called a

diode will be used. Obtain a 1N5062 (or equivalent) diode from your

local electronics supply company. A diode has two leads, an

anode lead and a cathode lead. The cathode lead is identified

by a band near that lead. Diodes will only allow current to flow

in one direction. We will connect the diode so that only the

excitation current will flow into the alternator's L connection.

 

An "S" connection which goes as close to the positive terminal

of the battery as physically possible. The "S" connection "senses"

the battery voltage and this is the voltage that the regulator is

tying to control. This connection has a high impedance, so it only

draws only micro amps from the battery, so it can be left connected

without fear of battery discharging.

 

The "L" and "S" connections are in the plug connector on the rear

of the alternator that looks like the capital letter "T". The top

of the "T" is the "S", and the other part of the "T" is the "L".

 

An "A" terminal, which is the output of the alternator, which

also is connected to the positive terminal of the battery. This

connector carries the charging current. Because of the high

currents this wire must carry, it is a low gauge wire, which means

it has a large cross sectional area. For safety reasons, a fusible

link should be in series with this connector. The "A" terminal is

the insulated threaded stud on the rear of the alternator.

 

Of course, someone may ask: "Why do you need two separate (the "S"

and the "A") connections between the battery and alternator?". It

is because of the fact that even large wires have some resistance,

and therefore there will be a voltage drop between the alternator

and the battery when the battery is being charged. If the regulator

sensed the alternator output (which is higher in voltage) and not

the battery terminal, the result would be undercharging of the

battery. Now there are alternators which work this way, but they

need a fairly large diameter charging wire to reduce the voltage

drop. The separate "S" connection is a much better method of

regulation.

 

BTW, There is a "P" terminal on the 280ZX turbo alternator (but I

have also seen it on a few of the non-turbo 280ZX alternators).

There is not a corresponding connector on the engine harness to

mate with the "P" terminal, even on the turbo 280ZX's. So, the "P"

terminal is not used/needed.

 

Finally, there is a ground connection on the alternator, although

the case is a pretty good ground connection to the engine block.

 

 

Procedure

 

Now, the following procedure only applies to the 240Z. The 260Z has

electrical connections between the regulator and the interlock

module and the electric fuel pump, so it's more difficult to

convert to an internally regulated alternator.

 

1. Disconnect the battery.

 

2. Unplug the external regulator and note the color code of the

wires that are on the regulator connector of the engine wiring

harness. You will be connecting some of these wires together, so

get another plug from a junked regulator or cut the one off your

old regulator. Now the wire colors I will be referring to are on

the regulator connector of the engine wiring harness. This is

because although the regulator wire colors match the engine harness

with the stock regulator, I've noticed that some aftermarket

regulators have a different wire color code.

 

3. Connect the white wire to the yellow wire. This connects the

battery to the "S" input.

 

4. Connect the anode of the diode to the black with a white

stripe wire and the cathode of the diode to the white with

black stripe wire. This connects the "L" terminal to a switched

12V supply through the diode preventing reverse current from

flowing.

 

5. Disconnect and unbolt your old alternator. Bolt up the new

alternator. Depending on what particular internally regulated

alternator you use (I've seen different pulley sizes), you might

need a different length belt.

 

6. At the alternator, connect the white with red stripe wire of the

engine wiring harness to the threaded stud (the "A" terminal) on

the alternator. This connection provides the charging current for

the battery. Connect the black ground wire to the alternator. Don't

forget to include any bypass, or filter capacitor. Plug the two-pin

"T" connector into the alternator.

 

7. Re-connect the battery and start the engine. With a good digital

voltmeter measure the voltage directly across the battery

terminals. This is the charging voltage. It should be 14.7V +/-

0.3V, but this voltage is a function of the ambient temperature and

the state of charge of the battery. If the voltage reading is not

correct, then re-check your wiring. More than 15.0V indicates that

the "S" connection may not be connected correctly.

[COZY Z COLE]

zcarnut...I see your procedure is at the bottom of one of this sites car tips. Very good write up.

 

http://www.atlanticz.ca/zclub/techtips/alternatorswap/index.html

 

 

LARRY

[EZ-E]

That is a good write up but if your going to use that, you might as well upgrade to the maxima alternator and have 95 amps.

 

Seems the better option.

[zcarnut]

That is a good write up but if your going to use that' date=' you might as well upgrade to the maxima alternator and have 95 amps.

 

Seems the better option.[/quote']

 

The above procedure is the same for the Maxima alternator (in fact I came up with the procedure in order to use the much higher rated Maxima alternator). The Maxima alternator has the same "S" and "L" terminals--it just uses a different type of electrical harness connector.

 

When viewing the Maxima connector on the alternator with the key on top the S terminal connection is on the left side and the L terminal is on the right.

 

In general:

 

“A” is connected to the battery positive terminal through a heavy gauge wire

“S” is connected to the battery positive terminal through a smaller gauge wire

“L” is connected to a +12V switched (IGN) source through the diode

[jtmny1999]

thanks thats alot of help

[Daphur280]

can someone explain this with wire colors? i have a 83 turbo in my 240z with the alternator from the 83. . . what do i do??????

[Daphur280]

nevermind I'm an idiot i read further and figured it out