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Thread: No Charging from Alt 1972 Z

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    Question No Charging from Alt 1972 Z

    I have a situation will the car will not charge. Started with a bouncing amp guage, thought bad alt or voltage regulator, replaced both with new. No charging. Car will start and run on just the battery, accessories work. Fusable link at starter has continuity. Took replacement Alt back to parts store got another one (5 day wait) put it on, no difference. Tried old voltage regulator with new alt, no difference. I have continuity to the W/R to the fusebox. So I have old alt and regulator and new alt and voltage regulator. AMP guage will show negative if you turn on accessories but will not show a positive charge with any combination of parts. I looked for links on this and saw that 72s may have two fusible links, and one is at the
    alt. I have continuity through the wire off of the back of the alt. Am I missing something really simple? Suggestions please, we have a car show next weekend, I have not been able to drive all summer. I want to be out with the car this year.

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    Did you check the voltage at the battery? Does the amp gauge read correctly as accessories are turned on and off?

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    Battery is new, voltage is 11.97 now having messed and started several times with no recharge. Voltage drop at the battery matches with the AMP guage. Battery does not show additional charge from any combination of alt or voltage regulator.

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    Did you try the old alt with a new reg? Is the new Alt internally regulated?

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    Both of the new ALTs were externally regulated. I have tried the new voltage regulator with the old alt, no charge, no charge with old alt and old voltage regulator, no charge new alt and new voltage regulator, no charge new alt and old voltage regulator. I have a rough time believing the two new alts were both bad. Even my luck would not be that bad. The good news is that I can change an alt really fast now with all the practice!

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    Did you check the output of the alt at the alt directly. If there is nothing there your field connections might be an issue.

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    Yes voltage from the alt is 14.5 at 1000-1200 rpm, yet nothing getting to the battery, it is draining and not getting a recharge.

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    Registered User Walter Moore's Avatar
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    There is a fusable link between the alternator and the wiring harness. It sounds like either that link is blown, or not hooked up properly.
    '71 240Z, Because any fool can drive fast in a straight line.

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    Where should that fusible link be Walter? I have no idea where it is? I cannot find another link other than the one on the starter that is good. Any help would be appreciated, needs to be running, if its not I cant sell it and i am done with this car. I thought the Lucus wiring was bad in UK cars this thing takes the cake!

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    Registered User Walter Moore's Avatar
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    The black wire that actually connects to the output terminal of the alternator is a fusible link. (According to the FSM) It connects to a White/Red wire (which is one of the largest gauge wires on the car by the way.)

    You should have +12V on the B+ (output) terminal of the alternator with the engine off. If you don't you have a break in the wiring. I suspect the fusible link is open, or you have a broken wire in that area.
    '71 240Z, Because any fool can drive fast in a straight line.

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    No wonder I cound not find it, it is not there, the W/R wire connects directly to the alt. so I guess somewhere along the life of this car it was removed. I have continuity through that wire to the fuse box. Thank you Walt, the archives just say it is by the alt, no description, so I appreciate your time.

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    Continuity from W/R to battery, when all connected I show the same voltage at the Alt connect as at the battery. Checked ground circuit, I have continuity through the line. Added additional ground to negative to chasis, added ground from alt to chasis. No Charge. Disconnected all connections, tested alt output. Idle 3.48 1100rpm 4.86 seems very low to me.

    Question, this is alt 3, is something in the car eating them? What would destroy the alt instantly, I have never got a positive reading since the fluction on the amp started and I replaced battery, alt and voltage regulator.

    I had to walk away from it today, I am very fustrated, everything is torn apart testing and cleaning connections.

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    Try this with the car not running but in the on position and the positive terminal disconnected from the battery. Disconnect the posative feed from the alternator and run a wire from the batter positive to the alternator wire and test to see if you get power.

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    Took the alt off yet again and took it to two different parts stores for testing. The alt is putting out 14.68 volts. Now I know beyond a doubt it is not the alt, so it is either wiring or votage reg.

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    You need to see where your voltage drops are with the alternator in place in the running engine. That will tell you where you've not got continuity. Connect the (-) probe of your multimeter to the case of the alternator (E terminal), and probe the following:

    -- Engine block (should be almost exactly 0 V)
    -- (-) terminal of battery (should be almost exactly 0 V)
    -- (+) post of alternator (should be approx 13.5 - 14.5 V if voltage regulator is regulating correctly)
    -- each side of the fusible link (should be same voltage as (+) post of alternator)
    -- (+) post of battery (in theory should be the same as alternator pos post, but might be a fraction of a volt lower)

    Any deviation from your expected voltages will reveal the trouble spot(s). Wherever you've got a suspect connection, measure the voltage across it. It should be 0 V. If you have a voltage greater than that, you've got a bad connection.
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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    The fusible link for a 72 Z is between the Starter's POSITIVE Batterty connection and the wiring harness. You should be able to see it below the battery going to the wiring harness on the side of the engine bay.
    Click image for larger version. 

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    As far as I know, there is only ONE fusible link in the 72's. If your car has the Intermittent Wiper (4 stops on the Comb Sw. ON-INT-LO-HI) then your car has 73 wiring and not 72.

    Check the connections at the battery, make sure you've cleaned the clamps and posts, also the grounds. You've added grounds and changed components, that's all good, just make sure everything is proper. Is the V/R mounted on the firewall or is it floating loose? How about the Amp Gauge? Good connections there?

    Also, I remember reading about another Z's Alternator NOT putting out proper voltage unless a certain RPM was maintained, are you idling or are you checking at higher RPM's?

    Are you making all these checks with all electrical systems off?

    How about your battery, is it fully charged? A "new" battery oftentimes needs a good external charger to bring it up to voltage, your Alternator will normally re-charge what you take out, but it takes forever to bring a Battery up to full voltage.

    FWIW
    E
    71 240 920 Gold
    72 240 Orange
    73 240 Red
    67 1600 Sports Roadster Spicy Orange Mica
    68 2000 Sports Roadster Red

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    Problem Fixed

    After going through the entire charging system, 3 alt, 3 voltage regulators, every wire, every connection, every fuse and adding grounds plus cleaning all the factory grounds it is charging. I decided to take the old voltage regulator that had been on the car since the 1980's (at least) and see if I could make it work. I took it apart, melted off the old solder, replace the wires, re-soldered, took the plug apart, replaced the wires and connectors. I hooked it back up with the alt that I had tested yesterday and low and behold the amp guage swung to the + side for the first time in months!

    I have no idea if the new voltage regulator is good or not, don't care now I have charging. Went on several 15 mile runs, and it charged like it was supposed to, even get the bob when the directionals are on at a stop light.

    Thank you for you assistance, all the testing and ideas may not have solved the problem, but I bet this car hasn't had the electrical system in this good of shape in since it left the factory.

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    Just make sure your alternator is running at the right voltage! You don't want anything higher than maybe 14.6V. (Even that's a bit high, but I think Datsun liked to run their voltages high-ish.)
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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    I sort of had a smiliar problem and it turned out to be a bad pully.

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