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So I installed a 280ZX alternator in my 240Z


Walter Moore

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As I have mentioned in other threads, when I originally put my 240Z back together I installed a GM style "Single Wire" hot-rod alternator in place of the 40A externally regulated unit. Well, that silly thing died recently, and since I really need the car operational next weekend, I decided to do the ZX upgrade described here: http://datsunzgarage.com/engine/

I went to the local Advance Auto, and ordered an alternator for a 280ZX Turbo, because they are supposed to be 70A units. I am not sure that is really what I ended up with, but the test report that was taped to the rebuilt alternator shows a maximum output under full load of 72A at 13.5V, so I was happy to see that.

I followed the Z Garage directions more or less, but at first I thought he was full of it. The connector to my voltage regulator didn't have all of the wires that he described. THEN I remembered that one reason I went with a single wire alternator in the first place was that some of the wires from that connector broke off when I unplugged it.:stupid:

So, after tracking down the missing wires, and determining their purpose, I was ready to follow the instructions, well almost.

I determined that the white and yellow wires he says to jumper are for the remote sense circuit, which being a very good thing I jumpered as instructed. (After finding said white wire lurking around the wiring harness...)

But, since I really hate soldering while standing on my head inside an engine compartment, I installed the diode in the jumper from the black w/white stripe wire to the white w/black strip wire. The black/white wire is from the ignition switch, so the diode needs to be installed with the "stripe" on the side connected to the white/black wire. This is much cleaner and simpler than hacking up your wiring harness.

Upon starting the car, the first pleasant surprise was that the alternator immediately put out 14V, even at idle! (on my meter that I added to the dash) The single wire unit would never start charging until I bliped the throttle to get its excitation voltage started. Even at that, it didn't like to produce 14V until the engine hit about 1K RPM.

However, my fears turned out to be justified in that with all the electrical accessories running, i.e. Headlights on high-beam, fog lights, driving lights, electric radiator fans, passenger compartment blower, wipers, etc. the voltage falls to less than 12V regardless of engine speed.

I guess it is usable for now, so long as I don't need to drive very much with the defrosters running at night in the rain.:(

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I went to the bone yard , found a 84 Maxima pulled the alt, used Dave Irwin's plug and play in the harness . At idle she never goes negative even with 90/100 head lights and every thing else on. It's a 90 amp. alt and the pulleys do not need to be changed , just a bolt on and go. $32.00

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Maybe it is just where I live, but I have had only bad experiences with parts from junk yards. Either they are broken to start with, or they don't last more than a year. To make matters worse, often the prices are higher than the what discount stores charge for rebuilt parts.

There are also a lot fewer junk yards around central Indiana than there were 20 years ago. I guess the increasing land values drove them out, or everyone else had the same bad experiences that I did.

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Just a curiousity based question. When those of you that have 240Zs upgrade to an internally regualated alternator, do you have any problems with the ammeter? In my old 320 pickup, after an alternator upgrade, I fried the stock ammeter and later an aftermarket one. After installing a voltmeter, I never had any further problems.

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I have been fighting this battle for about a month. The ammeter reads in the negative and the battery does not charge, when i put a voltmeter on the battery it shows that I have 14.2 volts. I had the alternator rebuilt, and the ammeter still shows "-". I am thinking now that I have fried the ammeter. Stephen what was your symptoms when you fried yours? If anyone has a voltmeter fuel gauge from a 78 280 Id be interested to getting it.

Dave

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No problems at all, my ammeter works perfectly. What type of device generates and regulates the current should have no effect on an ammeter, all it does is measure the current flow.

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The previous owner of my car did this upgrade, and the ampmeter sort-of "vibrates" around the center mark. Is this a problem? If so, what's the fix?
Sounds like a regulator issue to me. My ammeter is rock steady with the 60 amp ZX system. Far more steady than with the original alternator and points-type regulator. Was the original regulator properly by-passed?
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Is the 78 voltmeter/fuel gauge just a drop-in conversion from the stock 71 style ammeter/fuel gauge, or are there more considerations? I really want to upgrade my stock alternator. Thanks.
I doubt that it's a 'drop-in' but I'm sure it can be done. The plugs and wire colors will likely be different. Maybe the fuel gauge will hook up easily enough but you'll need to do some modification to the wiring to switch from a ammeter to a voltmeter. I have a 76 volt/fuel gauge. I have no clue if it works or not. I can look up the specs in the FSM and try to test it. I have no use for it. You can have it for postage if you'd like to experiment with it.
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I have a 76 volt/fuel gauge. I have no clue if it works or not. I can look up the specs in the FSM and try to test it. I have no use for it.

Just an observation, this would be the gauge to use in the 240's - for model years '77 and '78, they changed the font of the numbers / lettering on the gauges. The '76 matches the style of the 240 fonts.

Of course, the '75 has the same fonts but that is still an amp gauge....

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Thanks, sblake01! I would absolutely like to try it out. It's also good to hear from wal280z that the fonts would match. I forgot about that. So by all means PM me your info and I can PayPal you, USPS money order- whatever works best for you. No rush- I just bought another crate of parts from Black Dragon, MSA and Courtesy, waiting for the next rainy day. The only real unknown is whether the gas sender will dance nicely with the gauge. But then again my speedo reads almost 15mph too slow at 75. It never ends.

The alternative I'm also considering is changing all 3 of the smaller existing gauges to a new set, consisting of gas, voltage, and oil press/water temp, and ditching the clock.

I'd sorta rather not go there, as my Z is 100% original as came from the dealer- except for the transplanted 5-speed, tires, a Fiamm Ferrari triple airhorn (switched allowing either a "city"- neep neep or "country"- the loud HONNNNKing horn) and the radio/speakers. I even still have the horsehair padding and original carpeting/luggage straps, etc! But exchanging one Datsun OEM part for another is OK in my book.

Unfortunately I'm afraid that will set off the usual chain of events- WIAI- and then I'll end up changing the tach and speedo too, then I'll swap the illumination to EL, and pretty soon I'll have strobes, valve stem LED's, lighted washer nozzles and under-car cold cathodes too! Yuck. Although I can see adding a small CCD pipe to the dome housing- as seen here. :D

Please make it stop!

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Hi all, how about when you step on the brakes the guage shows more draw. Is that just a dirty taillight ground? My headlights get dim during idle also.
If the battery is fully charged, the charging system is working properly and has enough capacity, the ammeter should be steady and just barely to the + side whenever the load is stable. Adding any load (stepping on the brakes, turning on lights, radio or fan) should bring a brief dip to the minus side, then return to near zero.

Remember that all the ammeter does is show the difference between the regulated output from the alternator and the amount of current flowing through the various electrical bits. So if the battery is charged, and the alternator is keeping up with the load, it should be at or near zero. If it shows a steady negative draw, the alternator is either not working, or can't keep up with the load. Test this by turning on the lights with the engine off.

If the ammeter shows a steady + charge, that can mean a couple of things. One is that your battery is partially discharged, and the alternator is supplying more current than is presently needed in an effort to recharge the battery. The other cause could be that one or more operating electrical devices have been added (or re-wired) that pull their power off prior to the ammeter connection. (Those of us with Dave's relay harnesses have seen this one, as they pull direct from the battery, not through the alternator.) This is one reason that ammeters were replaced by voltmeters. The voltmeter captures the effects of all accessories, not just the ones wired to pass juice through the ammeter.

An ammeter needle that jumps when the load is steady indicated a voltage regulator issue. The old points type regulators would do this a little by nature, but an internal electronic regulator should react faster than the needle can and should be steady.

Lights that dim at idle is an indication of either too much resistance in the headlight circuit, or insufficient alternator output at idle. Both issues are common on 240Zs especially, and the headlight circuit resistance can be very troublesome, leading to melted fuseboxes and burned wiring harnesses.

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I doubt that it's a 'drop-in' but I'm sure it can be done. The plugs and wire colors will likely be different.

You are correct. It is not a drop-in and requires a bit of rewiring. The 240z gauge lights, for one, ground on the gauge housing. The 280z gauge lights have an actual ground wire that you need to connect to a ground.

The ammeter has the white and white/red wires that connect on either side to show the charge state. When installing the voltmeter, you need to connect these two wires together, completing the circuit that the ammeter used to complete. You can pull your voltage source for the voltmeter off this connection as well.

The fuel sender can be wired right up, but you will have to attached your own connectors. The 280z gauge has a plug with all of the relevent wires (lights, fuel, voltage, charge light, etc.) that the 240z does not.

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  • 6 years later...

I realize this is an extremely old post..  

 

I am in the process of trying to start an L28 in my '72 I rebuilt over the past few months.  I'm running a 280zx alternator upgrade with the custom adaptor wiring plug from MSA.  While priming the oil pump (ignition unplugged), cranking over, we noticed smoke coming from the cabin.  After tearing the heater panel out I see that the BLACK wire that runs to my ammeter/fuel level gauge is toast/burnt/fried/kaput.

 

I've been looking through my full color 240z wiring diagram, but they all show an ammeter/water temp gauge, not a amm/fuel gauge, so I'm a bit lost as to how to move forward and why that ground in particular would get so hot unless it was related to my new 280zx alternator. 

 

Attaching photo of the plugs on the alternator just in case you guys see something I am missing.

 

post-27965-0-86190600-1426721303_thumb.j

 

On the following site: http://www.zcarz.us/TechnicalInformationPageEngine&BodyElectrical.htm .. It reads that the stock ammeter won't work after the alternator upgrade, but not working would be an improvement over burning up my wiring harness.

 

Below is a shot of the fried wire from the ammeter gauge harness...

 

post-27965-0-75106900-1426722277_thumb.j

 

....and also the 280zx voltage regulator diode connector.

 

post-27965-0-31060400-1426722233_thumb.j

 

Many thanks in advance..

 

~Cameron

Edited by cnwayland
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Take a meter and find out which way is shorted - through the alternator's T plug or through the meter.  Then find out how the battery current is getting to the short circuit.  It's either shorted all the time, or when the key is On, or when the key is at Start.  Hopefully you were able to stop it before the wire was destroyed.

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Blue, thanks.  I've been following that thread as I noticed it was at the top in a timely fashion.

 

I noticed I'm not running a capacitor on either the harness side (where the regulator was disconnected) or the alternator side.  I read that most don't run them as they only filter out static in the wire.  I'm hoping that's accurate as I successfully tossed the old ones. 

 

Zed,

 

The wire is not totally destroyed but it is pretty toast.  I need to trace it back through the loom to see how far it was affected.  It certainly got VERY hot.   I'm not sure how to test for a shorted circuit in the ground system ~ but I am sure that there wasn't any issue until I was actually cranking the motor over.

 

Any information on how to read my wiring since the gauges seem to be from a differing setup than all of the '72 wiring diagrams I've found?  The ammeter seems to ground with the other gauges at the wiring harness that grounds near the starter?  My starter is grounded to the wiring harness's ground point on the right frame rail through a grounding strap.

Edited by cnwayland
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 but I am sure that there wasn't any issue until I was actually cranking the motor over.

 

My starter is grounded to the wiring harness's ground point on the right frame rail through a grounding strap.

If you're positive that this is the case, then it's a clue.  It would be odd though.  

 

You're not looking for a shorted circuit in the ground system.  You're looking for a short circuit to ground on a wire that should have resistance on it.  "Short circuit" just means that current is following a path back to the battery or alternator ground that it wasn't meant to follow.  A short cut.  Test all of the wires, they should all have some resistance on them, in the tens of ohms at least.  The shorted wire will have close to zero ohms resistance.

 

I'm not sure what that last sentence since the starter grounds through the mounting bolts.

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I'm not sure what that last sentence since the starter grounds through the mounting bolts.

 

I attached an image of the ground strap:

 

post-27965-0-25798000-1426743052_thumb.j

 

Zed, I'm trying to wrap my head around the signal flow and the short-cut explanation helps.  I found that the '71 has the similar gauge setup with FUEL/AMMETER ~ and I'm praying it's the only thing that shorted.  I'm not 100% sure that it's happening only under starting.  I need some more experience with my multimeter to accurately know what I'm testing for.

 

Additionally, after reading through the link http://www.classiczc...ons-w-pictures/ Blue posted, I'm wondering if the issue is related to the electric fuel pump I installed utilizing the stock wiring harness...  

Edited by cnwayland
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