I'm having issues with my 1978 280z the gauge inside the car just stays at 9 volts and doesn't go up, the battery is new (red top optima) and the alternator is also new. Where can I start checking to see if its just me or if theres something not allowing the alternator to charge? The fusible links have been upgraded and everything seems to check good. I have cleaned all of my connections but still nothing,Any suggestions will be appreciated. Thanks

what are you reading across the battery with a meter?

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Edmonton, Alberta, Canada.
My main areas of knowledge involve the ZX.

Grammar Saves Lives! IE: Lets eat Grampa or Lets eat, Grampa.

I'm reading around 12.4 volts, like I said the battery is new and I have also changed out the battery with my daily driver battery and both read the same at the gauge and also read 12.4 at the battery. How can I check to see if I have a bad voltage regulator?

run the meter on volts dc in the circuit from the alternator to the battery.

Tests can be found in the factory service manual. It's free to download at www.xenons30.com if your car is the 78 year model.

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Edmonton, Alberta, Canada.
My main areas of knowledge involve the ZX.

Grammar Saves Lives! IE: Lets eat Grampa or Lets eat, Grampa.

Start the car and test the voltage at the battery. It should be higher than when not running. I would say about 14 volts when running and 12 when not.

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1978 Datsun 280Z(near mint) bone stock
1976 280Z sold
1975 280z sold
1977 and 1980 Porsche 924 sold
1949 Studebaker R10 pick-up 70k mostly original)
1976 Lincoln Mark 16k (all original)
1972 Buick GS 455 4spd (frame off resto)sold

1. Make sure BOTH small wires behind the battery have 12 volts, when the car is running. 2.Make sure the "batt wire" from the alt to the battery is solid and has all it's strands. REMEMBER YOUR 78Z alternator has an INTERNAL voltage regulator. NK



Edited 1 time(s). Last edit was february 07, 11:01pm.

Thanks Norm. Wasn't sure on the earlier z's if it was internal or external. It also means he can run a volt dc meter in series witht the wiring from the alternator and see what the output from alternator to battery is.

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Edmonton, Alberta, Canada.
My main areas of knowledge involve the ZX.

Grammar Saves Lives! IE: Lets eat Grampa or Lets eat, Grampa.

Yes, both the ground and (+) battery cables are new, i'm replacing all the ground cables like the ground cable that connects to the firewall to the battery, and other grounds that connect to the engine also the ground that connects below the afm. Like I said if its a ground cable i'm replacing it, but i'm still not getting a charge,I might just take the alternator out and have a auto parts store check it for me.

SO did you check for voltage on the 2 small wires in the rear of the alt? A bright test-light on both is enough to see if you have it or not. Stab away. And yeah Easyguy, 78 was the first alt with internal v. regulator. NK

If you have trouble diagnosing it, take it to a shop and have them test the charging system. Paying for a diagnostic test is well worthwhile.

I went thru this with my ZX just last summer. You can search it out. Got the alt at AZ summer of 08. It lasted a year and crapped out last summer. I was reading 12v running and by the time I got home it was 10v. It seemed turning on the lights really did it. But I went thru 2 AZ alternators each that lasted 2 weeks before I got my money back and went to O'Reilly. 2 weeks later I had to return that one. So far so good. The weird thing is they would test good on their bench test.

So it is possible, even though new, your alt is bad.

Charge the battery and you voltmeter should say 12.x volts. With it running it probably will not get to 14, if even close. Keep an eye on it and see if it begins to fall. It usually took mine a couple days running in daylight, but once the lights came on it dropped like the stock market last week.

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Chattanooga, TN
82 white w/ red n/a coupe 120,000 miles.
83 2+2 314,395 miles at college AGAIN
96 Pathfinder, 96 Maxima
90 300ZX 2+2, 82 ZXcoupe, 81 200sx, 72 Camaro SS, 68 Mustang, 1950 Chev PU fully restored
Pics:[www.zcar.com]

Use an ohm meter, and remove each of your fusible links and test their resistance. It should be very low resistance. If not, the link might have overheated enough to cause a problem, but not quite enough to blow it open. Also, clean the fusible link contacts in the link boxes.

As you are doing, be sure that you have a tight, clean ground wire from the alternator body to the engine block, block to battery, battery to chassis.

The dash mounted voltmeters are notoriously inaccurate. On the ZX cars, it is adjustable with a small flat tip screwdriver. I think I read in this forum recently that the Z volt meters are also adjustable. If you measure correct voltage at the battery (12 to 12.5 vdc engine OFF, higher up to about 14.5 vdc engine idling) then the dash gauge might be either bad, bad wiring somewhere, or just needs to be slightly adjusted to match the "real world".

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Bob, in San Diego
1983 280ZX Turbo Coupe 5 speed

Visit [xenons130.com] for ZX Manuals, or
[www.xenons30.com] for 240Z, 260Z, or 280Z manuals.
Blue's Tech Tips [www.atlanticz.ca]
member Z Club of San Diego [www.zcsd.org]

*** Help stamp out "texting" abbreviations!!! ***

You know you can take your car to your local auto parts store, and they can do a battery/alternator/starter test for you for free, right? I know most of the Advance Auto Parts stores have a new tester that does all three at once for you, and it'll give you a print-out of all the information. Worth stopping in for if you're passing by one anyway.

I had this issue with my 78. Is the little light in the cars volt meter on? Does it ever come on? This bulb was burned out in my car and it wont excite the alt into charging if it is burned out.

The light does turn on when I first start the car on but my problem is that it doesn't seem to charge, I know that auto parts can check the car but my 78 is all in pieces, i'm getting ready for paint and its not driveable but I still like to turn the car on to move out of my garage.

If it is not charging, then can you not conclude it is the alternator. You can take the alt itself in and have it tested. There is a section in the FSM that tells how to test and repair it.

That said, I did my own on the 83. I had to replace the brushes and diodes and I think something else. The diodes went AFTER I replaced the brushes, so there was 2 removals. By the time it was done I had spent $55. Coulda got a lifetime guarantee at OReilly.

Of course that one is still going after 5 years. I went thru 5 at the parts stores just last year.

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Chattanooga, TN
82 white w/ red n/a coupe 120,000 miles.
83 2+2 314,395 miles at college AGAIN
96 Pathfinder, 96 Maxima
90 300ZX 2+2, 82 ZXcoupe, 81 200sx, 72 Camaro SS, 68 Mustang, 1950 Chev PU fully restored
Pics:[www.zcar.com]

Yes, I might just have to go that route, but I purchase the alternator a year ago and everything was fine, thats when I first installed it but you have to keep in mind that the car hasn't been driven neither but it was showing that it was charging i'm still working on the body and almost ready to paint it just wanted to make sure that once I paint it I can be able do drive it. I worked on several issues last year like the brakes upgraded to the toyota on front and put new pads and cylinders on the back, changed my fuse block upgraded it like they showed it in the atlanticz, put a new alternator, gas pump and fuel pump and finally I change out all the schocks and put the tokico adjustable along with struts. Just trying not to get discourage before I finish my project, so far it has been a learning experience. Thanks to this site I have been able to tackle all of this issues and I know that this issue is just of matter of me sitting down and playing around with the car but like always its good to ask for some advice because it has always help me to ask and also search. Once again thanks to everyone for taking the time and putting thier input, I appreciate it a lot. Thanks