Abdalla Posted October 7, 2012 Share Posted October 7, 2012 I'm doing the ZX alternator upgrade but I'm not getting a charge out of the new alternator. I followed the steps on: http://atlanticz.ca/zclub/techtips/alternatorswap/index.html. Here is my old Alternator: 76 280z New Alternator: 81 280zx Turbo And the wiring: After following the instructions, I plugged the car up to the jumper cables to start it and it fired right up. As soon as I disconnect the jumper cables. The car will idle rough and shut back down. Also, the charge light in the dash does not come on at all. So it seems to me as if the car is running off of the battery and not getting a charge for the alternator. My questions is, did I wire something wrong? I can't figure out if the yellow cable coming out of the new alternator needs to be used. Aside from the two cables that need to be spliced, are there any other cables I should be splicing? I did a lot of google searches and I searched the forum for a solution but I can't seem to find anything. Thank You, Abdalla Quote Link to comment Share on other sites More sharing options...
motomanmike Posted October 7, 2012 Share Posted October 7, 2012 (edited) On the T plug, did you make any modifications? The one that plugs into the back of the alternator? Test it with a voltmeter. Top of the T and bottom, one should have constant voltage,the other gets 12 volts from the key switch. I'll go out in the garage in a bit and look which ones. I didn't modify my old regulator at all just left it plugged in. Report back what readings you get where. Your alternator requires a "sense" the top of the T plug, I cut the wire, installed an eyelet, and bolted it directly to the main battery stud so it has constant battery power. It also has an "activation" wire from a 12volt feed, and i'm not sure on a 76 but I think will need an inline diode but i might be wrong I installed one on mine, without it the car would not shut off. Either way, the up and down portion of the T is your switch power, should be 12v when key is on, the diode should let power flow to the alternator so orient it accordingly. Your alternator is not activating. Your alternator will wear out faster if you do get it to activate and do not charge that battery on a battery charger before letting it loose on the alternator. Alternators are battery maintainers, not battery chargers. Your yellow wire coming out of the alternator is a "tach" terminal, typically is molded into the housing of the alternator but yours oddly enough is not. You will not use that wire. Edited October 7, 2012 by motomanmike Quote Link to comment Share on other sites More sharing options...
NewZed Posted October 7, 2012 Share Posted October 7, 2012 If your Charge lamp doesn't glow before starting the engine, that's a problem. It energizes the windings so that the alternator will start charging right away. Your Lamp, or L, wire must be disconnected. I think that it's white with a black stripe. It should have power only when the key is On. The yellow wire is the Sense, or S, wire. It monitors voltage so that the internal regulator will work correctly. Without it connected, I think that the alternator might put put maximum voltage (once you get the L wire connected). It has power all the time. If you follow the atlanticz directions for a 1976 car, the wire to the brake warning lamp check relay will have power all the time and your battery will die in a day or two. Better to just run the yellow wire directly to the starter positive lug or the battery post and tape off the end of the yellow wire. Then find a power source for the check relay that only has power when the engine runs. I used the fuel pump power wire at the connection under the passenger seat. That's where the relay is anyway also. Finally, starting a car with a dead battery is apparently a good way to damage an alternator. You should charge the dead battery first, or leave the cables on until the dead battery is charged. I wrote the above from memory of when I did my 76 and a look at the wiring diagrams on the atlanticz site, so be careful and double-check. Use a voltmeter. Quote Link to comment Share on other sites More sharing options...
Abdalla Posted October 8, 2012 Author Share Posted October 8, 2012 On the T plug, did you make any modifications? The one that plugs into the back of the alternator? Test it with a voltmeter. Top of the T and bottom, one should have constant voltage,the other gets 12 volts from the key switch. I'll go out in the garage in a bit and look which ones. I didn't modify my old regulator at all just left it plugged in. Report back what readings you get where. Your alternator requires a "sense" the top of the T plug, I cut the wire, installed an eyelet, and bolted it directly to the main battery stud so it has constant battery power. It also has an "activation" wire from a 12volt feed, and i'm not sure on a 76 but I think will need an inline diode but i might be wrong I installed one on mine, without it the car would not shut off. Either way, the up and down portion of the T is your switch power, should be 12v when key is on, the diode should let power flow to the alternator so orient it accordingly. Your alternator is not activating. Your alternator will wear out faster if you do get it to activate and do not charge that battery on a battery charger before letting it loose on the alternator. Alternators are battery maintainers, not battery chargers. Your yellow wire coming out of the alternator is a "tach" terminal, typically is molded into the housing of the alternator but yours oddly enough is not. You will not use that wire. I didn't modify anything on the T plug. I plugged it right into the new alternator. I'll test it with a voltmeter and report back. If your Charge lamp doesn't glow before starting the engine, that's a problem. It energizes the windings so that the alternator will start charging right away. Your Lamp, or L, wire must be disconnected. I think that it's white with a black stripe. It should have power only when the key is On. So I need to splice the L wire into something that only runs with the ignition on. If you follow the atlanticz directions for a 1976 car, the wire to the brake warning lamp check relay will have power all the time and your battery will die in a day or two. Better to just run the yellow wire directly to the starter positive lug or the battery post and tape off the end of the yellow wire. Then find a power source for the check relay that only has power when the engine runs. I used the fuel pump power wire at the connection under the passenger seat. That's where the relay is anyway also. Basically take the yellow wire and run it directly to the + on the battery or starter and the check really gets spliced in under the passenger seat? Quote Link to comment Share on other sites More sharing options...
Abdalla Posted October 8, 2012 Author Share Posted October 8, 2012 Alright so I went out and tested the T plug with a volt meter and here is what I got. At the yellow cable: At the white & black cable with ignition off: When the ignition is on, I get 12v. Here are the connections I have for those two cables: White and black cable is connected to the blue which is giving it power when the ignition is at the on position. Yellow cable I spliced into a new electric cable that is running directly to the battery. I'm still not getting a charge light at the dash board and the I'm pretty sure the car is still running off of the battery and not the alternator. All your help is appreciated. I'm not definitely a newb when it comes to wiring. Thanks! Quote Link to comment Share on other sites More sharing options...
NewZed Posted October 9, 2012 Share Posted October 9, 2012 Are you testing at the T plug or at the point you cut the old wire? Your results on the white/black wire are what you would expect for the L wire. No power with the key off, and power with the key on. The charge light should go on when it's grounded, assuming it's the right wire that comes through the lamp. If you have a test light, you could ground through the T plug through the light (to avoid a dead short if it's the wrong wire) and the charge lamp should glow with the key on. It's also possible but a little unlikely that the alternator does not have a good ground, or that it's bad. Check the ground through the alternator case. Power should come through the lamp, down the wire to the T plug and in to the windings then ground. Quote Link to comment Share on other sites More sharing options...
Abdalla Posted October 9, 2012 Author Share Posted October 9, 2012 Are you testing at the T plug or at the point you cut the old wire? Your results on the white/black wire are what you would expect for the L wire. No power with the key off, and power with the key on. The charge light should go on when it's grounded, assuming it's the right wire that comes through the lamp. If you have a test light, you could ground through the T plug through the light (to avoid a dead short if it's the wrong wire) and the charge lamp should glow with the key on. It's also possible but a little unlikely that the alternator does not have a good ground, or that it's bad. Check the ground through the alternator case. Power should come through the lamp, down the wire to the T plug and in to the windings then ground. No, I am testing the T plug at the alternator. I'm under the impression that the white/black wire is the L wire. Please correct me if I'm wrong. If I end up getting this thing to work, I think I might write a more dummy friendly write up lol. Quote Link to comment Share on other sites More sharing options...
Ben280 Posted October 12, 2012 Share Posted October 12, 2012 When I did this conversion in my car, I was having lots of issues, mainly with a factory splice in the white with red stripe wire coming off the alternator. (runs to a small ring terminal on the right side of the alternator). This is the wire that carries power from the alternator through the fusibale link system, into a the fuse box and charges the battery. The splice I replaced was about a foot from the alternator. If the battery isn't charging I would investigate this wire. Check and clean all your connections while your at it and check all your fusible links. I'm a little confused too by your statement of "not getting a charge light". The charge light in the voltage gauge should only be illuminated when the key is in the "On" position with the motor not running. If the light is off with the car running, then all is well within the charge circuit. If the light is illuminated all the time, something is wrong there! Check voltage across the battery and compare to voltage at the alternator. They should be within a couple tenths of each other, and generally around 14.5-14.8v If the battery is low investigate the above connections. Quote Link to comment Share on other sites More sharing options...
mattb3562 Posted October 30, 2012 Share Posted October 30, 2012 I just done this conversion on my 76 because I assumed that my stock alternator went out. It was so cheap to buy the new zx piece, I slapped it on and it changed nothing. I had not went thru the troubleshooting to discover that all that had went out was my charge lamp. You need to pull it out and check it for continuity if it doesnt come on with the switch in on position. 49 cent fix and havnt had any probs since. Quote Link to comment Share on other sites More sharing options...
Abdalla Posted November 29, 2012 Author Share Posted November 29, 2012 I totally forget about this thread. It turned out the alternator I had gotten was bad lol. Oops. Got it replaced and its been running great since then. I still don't get a charge light on the dash but the car has been running fine for a while now without it. Quote Link to comment Share on other sites More sharing options...
Pac_Man Posted November 29, 2012 Share Posted November 29, 2012 I totally forget about this thread. It turned out the alternator I had gotten was bad lol. Oops. Got it replaced and its been running great since then. I still don't get a charge light on the dash but the car has been running fine for a while now without it. Correct me if I'm wrong but shouldn't the charge light stay off if the car is running and the alternator is working? Quote Link to comment Share on other sites More sharing options...
motomanmike Posted November 29, 2012 Share Posted November 29, 2012 (edited) This is how I've got my hitachi alternator wired. Top of the T is the "sense" I have it jumped directly to the battery stud. Bottom of the T is the activation wire, I have a diode spliced inline and it gets power when the ignition is on. Edited November 29, 2012 by motomanmike Quote Link to comment Share on other sites More sharing options...
Abdalla Posted December 9, 2012 Author Share Posted December 9, 2012 Correct me if I'm wrong but shouldn't the charge light stay off if the car is running and the alternator is working? My understanding is, when you start the car you should get a charge light for a couple seconds. I don't get a light at all. I'm assuming the bulb is out. Quote Link to comment Share on other sites More sharing options...
carbondatsun Posted December 12, 2012 Share Posted December 12, 2012 My understanding is, when you start the car you should get a charge light for a couple seconds. I don't get a light at all. I'm assuming the bulb is out. lol oh abdalla your bulb is never out Quote Link to comment Share on other sites More sharing options...
gijohnny23 Posted February 19, 2014 Share Posted February 19, 2014 I know this is an old thread but I've recently done an 85 300zx alternator swap. The problem is it doesn't use the t plug but uses a newer nissan plug and although it seems to be ok I do not understand why with just a turn signal on I can hear my fuel pump change flow with the blinker. This symptom is what lead me to the think the alternator in the first place. I then followed the shop manual and found my alternator wasn't pushing enough volts out. Under the new system I get somewhere in the 13.7v across the battery when idling and I do get a jump in the amp meter then it goes back to just a titch above zero when cycling lights and other things. On top of the fuel pump I noticed the higher load I have the lower my idle. To the point it has died at stop lights. Now I understand the higher load buts more pull on the motor but isn't there a way to increase the idle while under load? Similar to when the ac is on? Or should I just adjust my idle to compensate? Also this is an almost completely stock 75 280z with the five wire voltage regulator. The fuel pump is aftermarket as well. Quote Link to comment Share on other sites More sharing options...
NewZed Posted February 19, 2014 Share Posted February 19, 2014 A few RPM can have a big effect. http://reconitelectric.blog.com/files/2012/03/alternator_power_curve.jpg Quote Link to comment Share on other sites More sharing options...
9rider Posted February 19, 2014 Share Posted February 19, 2014 I know this is an old thread but I've recently done an 85 300zx alternator swap. The problem is it doesn't use the t plug but uses a newer nissan plug and although it seems to be ok I do not understand why with just a turn signal on I can hear my fuel pump change flow with the blinker. This symptom is what lead me to the think the alternator in the first place. I then followed the shop manual and found my alternator wasn't pushing enough volts out. Under the new system I get somewhere in the 13.7v across the battery when idling and I do get a jump in the amp meter then it goes back to just a titch above zero when cycling lights and other things. On top of the fuel pump I noticed the higher load I have the lower my idle. To the point it has died at stop lights. Now I understand the higher load buts more pull on the motor but isn't there a way to increase the idle while under load? Similar to when the ac is on? Or should I just adjust my idle to compensate? Also this is an almost completely stock 75 280z with the five wire voltage regulator. The fuel pump is aftermarket as well. My 1975 have the same problems as yours. I could hear my pump change flow with the blinker , and died at stop light if I didn't rev the engine up enough.I have the 240sx 90 Amp alternator ready to swap in but my car is away from me at this moment, I will get it back next week and doing the swap and see if swapping new alternator will cure the problems. Quote Link to comment Share on other sites More sharing options...
m1ghtymaxXx Posted February 19, 2014 Share Posted February 19, 2014 Pretty basic, but have you checked your grounds? A corroded ground caused a myriad of problems on my 83, included sensitivity to load (voltage gauge would dance when the signals or wipers were going), overcharging at high RPM, eating through batteries and alternators, and eventually melting the fusible link box. Quote Link to comment Share on other sites More sharing options...
9rider Posted February 20, 2014 Share Posted February 20, 2014 Pretty basic, but have you checked your grounds? A corroded ground caused a myriad of problems on my 83, included sensitivity to load (voltage gauge would dance when the signals or wipers were going), overcharging at high RPM, eating through batteries and alternators, and eventually melting the fusible link box. I did check my ground. My alternator is dying. I can hear whining sound, using stethoscope I know it from the alternator not the engine. Quote Link to comment Share on other sites More sharing options...
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