kaito Posted April 20, 2012 Share Posted April 20, 2012 My charging circuit decided to quit on my way to work one morning but thankfully megasquirt will run even with 9 volts!! Anyways, I took my alternator to autozone to have it tested and the guy who helped me said it was good. I had them test my battery and it also passed. That would, with deductive reasoning, mean my voltage regulator is faulty. I then bust out the FSM and do a couple quick tests. First was obviously a ground check with the alternator body and chassis ground. That was good to go. Then I checked conductivity on the N teminal plug and voltage regulator. Have conductivity, so good to go there. I then remove the n terminal and start the car. I checked N terminal on the alternator at idle and revving. Only 8.3 volts. Not looking good. I also dont have voltage at all coming from the yellow N terminal wire to the regulator when the plug is reconnected. The FSM says that in both of these cases the alternator is suspect. So am I done troubleshooting or do I need to further investigate this? I want to get new parts, but only if I need them. What do you guys think? Quote Link to comment Share on other sites More sharing options...
beermanpete Posted April 20, 2012 Share Posted April 20, 2012 The N terminal is a center-tap in the stator and should be at about half the system voltage, so 8.3 volts is a bit high. The regulator will not provide voltage to the N terminal. The in-car test for the alternator is to full-field it and see if the system voltage rises. To do this remove the 2-pin connector from the alternator and connect the F terminal from the alternator to the battery. This will force the alternator to produce maximum output and the voltage should rise to as you speed up the engine. Be carefully not to race the engine because the voltage can easily go to 17 or 18 volt. If the voltage does rise as indicated the regulator is bad or there is a wiring fault. If not, the alternator is bad. Check the IG terminal (Black/white wire) going to the regulator, for voltage. It should be +12 when the ignition key is on and go to 0 when the ignition key is off. Quote Link to comment Share on other sites More sharing options...
kaito Posted April 21, 2012 Author Share Posted April 21, 2012 The IG terminal does what you said it should do. I just jumped the F terminal to the battery and it produces voltage which increases with engine speed. I guess autozone was right. Ill be buying a new regulator soon. Thanks so much for the help. You saved me money and taught me something at the same time. It was easy to wrap my head around the this test vs the FSM tests. Thanks again! Quote Link to comment Share on other sites More sharing options...
beermanpete Posted April 21, 2012 Share Posted April 21, 2012 Cool. Glad to help. Let us know how it works out. Quote Link to comment Share on other sites More sharing options...
kaito Posted April 22, 2012 Author Share Posted April 22, 2012 Just tried out a new regulator but no cigar... It was mentioned that the N terminals voltage was a bit high. Would the regulator not be putting out voltage for that reason? It might be a coincidence but this all happened after I installed a stereo, and after the stereo install my turn signals also quit. My hazards never worked but now they do. Anyways, Im thinking about just doing the cs144 upgrade. Quote Link to comment Share on other sites More sharing options...
Xnke Posted April 23, 2012 Share Posted April 23, 2012 You have a ground fault under the dash. Fix that, or you run the risk of installing a high-output alternator and high-outputing the entire car's wiring harness into flames. Quote Link to comment Share on other sites More sharing options...
kaito Posted April 23, 2012 Author Share Posted April 23, 2012 Thanks for the tip. Seriously. I don't want flames. I guess I will be taking the dash out to find it. I needed an excuse to remove it anyways. Not trying to ask for handouts or anything but you have any recommendations for where I should start? Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 23, 2012 Share Posted April 23, 2012 The alternator is on the same circuit as the battery so if you had a short the battery could short out too. The battery can pump out a lot more amps in a short time than the alternator can. If you don't have flames now, a higher capacity alternator won't increase the odds. Quote Link to comment Share on other sites More sharing options...
Leon Posted April 24, 2012 Share Posted April 24, 2012 Thanks for the tip. Seriously. I don't want flames. I guess I will be taking the dash out to find it. I needed an excuse to remove it anyways. Not trying to ask for handouts or anything but you have any recommendations for where I should start? With a wiring diagram combined with the BE section of the appropriate FSM. Check all grounds and pertinent electrical connections. Quote Link to comment Share on other sites More sharing options...
beermanpete Posted April 24, 2012 Share Posted April 24, 2012 Have you checked the voltage at the output terminal on the alternator? Perhaps the alternator is working but the output wire has been unhooked under the dash when you installed the radio. The wiring various with year. What year is your car? Quote Link to comment Share on other sites More sharing options...
kaito Posted April 26, 2012 Author Share Posted April 26, 2012 Sorry beermanpete, Ive been busy the past couple days and havent checked up on my post. My car is an early model 260z. The output post for the bat terminal on the alternator is not putting out voltage. Ill look into the output wire you speak of.Im in the process of checking all the grounds, looking for and identifying unknown loose wires, and removing the dash to check for all under dash wiring. I have also started the upgrade to the cs144 alternator and will be modifying the bracket, swapping pullies, and mounting the alt in the car today. Ill save the wiring till after I figure out the electrical gremlins. Quote Link to comment Share on other sites More sharing options...
kaito Posted April 27, 2012 Author Share Posted April 27, 2012 Just another question, I just did a resistance test on the yellow wire (sense) and I got readings on both pos and neg terminals. This is normal right? Also something has been bothering me for a couple of days, it was mentioned that I might have an under dash ground. After I did the radio install I noticed two wires that are red with a blue stripe. I Checked them and they both go to ground. I then saw when taking out the dash tach and speedo the same colored wires going to each lightbulb. They are definitely ground wires. My question about the red/blue wires is, where do they need to be connected and what are they for? Quote Link to comment Share on other sites More sharing options...
beermanpete Posted April 27, 2012 Share Posted April 27, 2012 Just another question, I just did a resistance test on the yellow wire (sense) and I got readings on both pos and neg terminals. This is normal right? Also something has been bothering me for a couple of days, it was mentioned that I might have an under dash ground. After I did the radio install I noticed two wires that are red with a blue stripe. I Checked them and they both go to ground. I then saw when taking out the dash tach and speedo the same colored wires going to each lightbulb. They are definitely ground wires. My question about the red/blue wires is, where do they need to be connected and what are they for? Yes, it is normal to get a resistance reading from the yellow wire to both the positive and negative terminals. The red and blue wires go to ground through the dimmer control for the meter lamps. These should not cause any problem with the charging system. Make sure the alternator has a good ground connection to the regulator (E terminal, black wire). Check the voltage at the F terminal. It should be close to battery voltage when the key is on but the engine is stopped. When the engine is running the voltage at the F terminal should fall somewhat as you speed up the engine. No or low voltage here indicates a bad regulator or a bad connection in the A terminal (white wire) between the alternator and regulator. Quote Link to comment Share on other sites More sharing options...
kaito Posted June 4, 2012 Author Share Posted June 4, 2012 I just wanted to touch base with this thread again. I never figured out the charging problem. I gave up and installed a rebel wiring chassis harness. Upon completion of the installation I had the same problem. Turns out the new alternator was bad even though autozone tested it good. Well now I know. Thanks again beemanpete for the help. Quote Link to comment Share on other sites More sharing options...
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