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Thread: 1976 280Z Alternator Upgrade - Minor Issue/Battery Drain

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    Default 1976 280Z Alternator Upgrade - Minor Issue/Battery Drain

    Made a mistake in my first post. Original and corrections shown below. Sorry for the messy post. Basically what I've found is that both of the two popular alternator conversion instructions will allow the alternator to charge, internally regulated, but they both leave loose ends for other components in the 1976 280Z.


    I am new to this site but thought I would share something I found out about upgrading to a 1979 ZX alternator on a 1976 280Z. Using the atlanticz.com instructions - http://www.atlanticz.ca/zclub/techti...wap/index.html - the brake warning lamp check relay will be "hot" all the time, even with the key off, since it is spliced off of the S line to the alternator plug. I found that the slight amount of current it draws would drain my battery after a few days. According to the FSM, California cars also have an EGR cut solenoid that would also be always energized. I assume that the old mechanical voltage regulator ran the S line and/or brake check relay through the ignition circuit (I did not dig in to confirm) so this was not a problem. You can tell if you have a similar problem after the conversion, if you hear relays clicking when you reconnect the battery, with the key off.

    Edit 11:41 am 11/12/09 - The following is wrong, it will not let the relay work correctly. The relay needs to be energized when the motor is running/cranking, but dead when the ignition circuit is on. {{{I fixed the problem by wiring the system like zcarcreations recommends - http://www.zcarcreations.com/howto/voltreg.htm - to get the relay back on to an ignition circuit}}}

    I ended up splicing the brake warning lamp check relay yellow wire, which energizes the relay solenoid, to the fuel pump circuit, which has a plug in the vicinity under the passenger seat. The fuel pump only runs when the motor is running.

    Edit 11:41 am 11/12/09 - This part still seems right {{{, but cut the S line splice off of the circuit and wired it direct to battery + terminal.}
    This also lets the alternator see mostly battery charge and not the voltage after the loads on the ignition circuit. I get a smooth 14.5 volts with the S line wired direct, but was getting a jumpy over 15 for the short time I had it wired through the the ignition circuit (measured with a good voltmeter at the battery).}}}

    That's all I have. I enjoy the discussions and hope this helps someone out if they decide to go with an internally regulated alternator.

    p.s. I also found that the dash voltmeter is pretty easy to adjust using the slotted adjuster on the back of the gauge.
    Last edited by Zed Head; 11-12-2009 at 12:01 PM. Reason: clarity

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    Quote Originally Posted by Zed Head View Post
    I am new to this site but thought I would share something I found out about upgrading to a 1979 ZX alternator on a 1976 280Z. Using the atlanticz.com instructions - http://www.atlanticz.ca/zclub/techti...wap/index.html - the brake warning lamp check relay will be "hot" all the time, even with the key off, since it is spliced off of the S line to the alternator plug. I found that the slight amount of current it draws would drain my battery after a few days. According to the FSM, California cars also have an EGR cut solenoid that would also be always energized. I assume that the old mechanical voltage regulator ran the S line and/or brake check relay through the ignition circuit (I did not dig in to confirm) so this was not a problem. You can tell if you have a similar problem after the conversion, if you hear relays clicking when you reconnect the battery, with the key off.

    I fixed the problem by wiring the system like zcarcreations recommends - http://www.zcarcreations.com/howto/voltreg.htm - to get the relay back on to an ignition circuit, but cut the S line splice off of the circuit and wired it direct to battery + terminal. This also lets the alternator see mostly battery charge and not the voltage after the loads on the ignition circuit. I get a smooth 14.5 volts with the S line wired direct, but was getting a jumpy over 15 for the short time I had it wired through the the ignition circuit (measured with a good voltmeter at the battery).

    That's all I have. I enjoy the discussions and hope this helps someone out if they decide to go with an internally regulated alternator.

    p.s. I also found that the dash voltmeter is pretty easy to adjust using the slotted adjuster on the back of the gauge.
    I put a 76 voltmeter in place of the ammeter in my 71 and wired the charge light to a switched ignition source. I later changed the charge light to a red LED. My altermator is a internaly regulated GM CS-144.

    Dave...

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    Thanks for the reply Dave. I made a hash of my first post though, (see edited). Realized that the job was only 80% done...

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    In looking back at this post, I realized how hard it is to understand. Here is a simplified rewrite, from memory (so please confirm wire colors and check power before cutting or splicing anything).


    If you use the atlanticz.com alternator upgrade procedure on the 1976 280Z you will need to cut the yellow wire that goes to the brake warning lamp check relay under the passenger seat and resplice it in to a wire that is hot only when the engine is running. If you don’t the relay will be connected directly to the battery when you are done, therefore will not work correctly, and it will also slowly drain your battery. The brake warning lamp check relay is only supposed to have power when the engine is running.

    You can tell if you have this problem if you hear relays clicking when you reconnect your battery.

    The closest and easiest power source is to the fuel pump power line, which conveniently has a junction at the connector that runs next to the rocker panel also under the passenger seat. It is shown on page BE-7 Detail A in the FSM. I cut the wire to the relay, crimped on a flat male blade connector and inserted it in next to the GL wire in the connector. The fuel pump is only powered when the engine is running (unless you have wired it direct). I also put a 10 amp fuse inline so I wouldn’t fry any extra wiring if the relay shorted out (there were high water marks under the seat from previous ownership).

    Don’t forget to insulate the end of the yellow wire since it will still be connected to the battery. Or you can dig in to the wiring harness in the engine bay, find the splice and cover it up there. I think it is spliced in to one of the red and white wires.

    In the short term, if you just cut the wire to the relay but don’t repower it, the car will run (assuming it did before you started), and the battery will not discharge, but the brake warning light in the speedometer won’t show that your parking brake is on and it won’t show when you have a brake system pressure imbalance. I hooked mine back up to avoid that smokey burning smell, plus it will tell me when the next wheel cylinder leaks out.

    If you have a California car, you might find a similar problem with an EGR cut solenoid(?), from what I can figure out from the wiring diagram.


    If you use the zcarcreations.com procedure, the battery will not drain but the brake lamp in the speedometer will not go on when the ignition is turned on before starting the car like it is supposed to, to show that the lamp is working.

    I hope this makes more sense.

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    I JUST did the alternator conversion on Thursday and after having the car sit from Saturday to this morning, I came out to find it completely dead. The Z community here and on HybridZ is absolutely amazing as you all came together and got me this information.

    I had my sister repeatedly touch then remove the battery terminal until I could find the offending relay. For the sake of being awesome I took a picture of the damn thing!



    I can live without the various things it's supposed to do for a couple days. I'll figure out where it wires into come Friday or something.

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    So the alternator mod has been running awesome for a while now with one exception.

    When idling, or even occasionally while cruising down the freeway, the alternator will stop charging. It's usually brief, and a change in RPM will get things working again.

    Anyone have any idea? The only wire I have directly to the battery is the charge wire; think running a direct S wire might help?

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    "It is shown on page BE-7 Detail A in the FSM"

    What/Where is the FSM?

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    Quote Originally Posted by awolfe View Post
    "It is shown on page BE-7 Detail A in the FSM"

    What/Where is the FSM?
    Here ya go.

    http://www.xenons30.com/reference.html

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    Hey guys I know this thread is a bit old but I just recently discovered that the PO of my 77 did the 60 amp alternator swap from a zx, and it was wired incorrectly. I rewired correctly and car ran fine for first couple months now every time I start the car it has to be jump started. Not sure if its the battery or alternator but the volt meter is reading about 13 volts with the car off. here is the strange part, I disconnected both of the relays under the passenger seat but for some reason the brake warning lamp and volt meter light still come on while key is in on position like theyre supposed to and turn off after the car is running, any thoughts?

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    My old thread, back to life!

    If the rewire worked for a couple of months, I would have the battery and alternator tested, or test them your self by disconnecting either and seeing if the drain stops. A shorted alternator will drain the battery and a bad battery might not take a complete charge. And check the remaining wires from the conversion, one of them is hot all the time on the 76. It might be shorting to ground.

    No idea about the relays not affecting the brake warning light. Maybe Nissan moved the relays in 77. Odd. You did mention one other thing that's not quite normal - the voltmeter should be on all the time not just with the key on. But that might not matter.

    Assume that your car is normal and check the normal stuff for a battery drain, the battery and alternator.
    1976 280Z, with some minor modifications

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