Muskrat Posted January 18, 2004 Share Posted January 18, 2004 I just got back from getting my internal reg. alternator test at my local Autozone. I am unsure as to exactly what car this alternator came out of, only that it came with, thought not attached to, the engine I bought from All Z. It has the T shaped plug connection and lacks a "P" connection. The test machine came up with something like 16 volts, but a light came on indicating that the alternator has a diode burnt out inside the unit. The alternator was intended to go into my 240z sometime before my engine swap, which I understand will need a diode installed so that the key will actually turn the car off. Could anyone exlplain this? Quote Link to comment Share on other sites More sharing options...
Xander Posted January 19, 2004 Share Posted January 19, 2004 The diode you need for shutting the engine off has nothing to do with the diode they measured. There are a couple of diode in the back of the alternator to rectify the AC it produces. If one is busted then the alternator will work but will not put out the power you require. I think you need an alternator rebuild. Quote Link to comment Share on other sites More sharing options...
Muskrat Posted January 19, 2004 Author Share Posted January 19, 2004 Thanks, that exactly the info I was looking for. Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted February 7, 2004 Share Posted February 7, 2004 xander... i'm curious about this... i need to go look it up... but what exactly is the definition of a diode? is it a kind of relay or a kind of voltage regulator? Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted February 7, 2004 Share Posted February 7, 2004 Alright so correct me if i'm wrong but from what i just looked up.. a diode is basically used to steady the current from the altenator turning negative pulses into half positive waves. something like that? -Ed Quote Link to comment Share on other sites More sharing options...
SpeedRacer Posted February 7, 2004 Share Posted February 7, 2004 A diode is a one way switch. It will allow current to pass through it in one direction but not in the opposite direction. In the alternator they are used to change the alternating current (AC) to direct (DC) current. In an automotive alternator there are usually six of them - three positive and three negative. Quote Link to comment Share on other sites More sharing options...
Muskrat Posted February 7, 2004 Author Share Posted February 7, 2004 Good general knowledge information there. That alternator is really just a boat anchor now, I'm picking up a 125 amp unit from a 95 Maxima tomarrow morning. Quote Link to comment Share on other sites More sharing options...
Xander Posted February 7, 2004 Share Posted February 7, 2004 Sorry Nismo I missed your question. As Speedracer said a diode is basically a one way checkvalve for electronics. And it has a fixed voltage drop of 0.6 volts. U can use this when you want to up the voltage to the battery. A internally regulated alternator has a sense wire. The alternator will try to keep the voltage of this wire at about 14.4 volts when runing. Usually the sense wire is a battery plus. But if you wire a diode inline with the sense wire, you can up the battery voltage by 0.6 volts. Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted February 8, 2004 Share Posted February 8, 2004 So if i were to go to radio shack to buy diodes for my car. I would be looking for what exactly? something handling 16 volts min. Would it work inline, or does it have to connect the output wire to the ground wire? btw.. my gauges read aroudn 16 volts maybe a tid bit more when running gonna put a meter on it tomorrow. -Ed Quote Link to comment Share on other sites More sharing options...
Muskrat Posted February 8, 2004 Author Share Posted February 8, 2004 NismoEd, if your gauge is reading anything much above 12 volts with the car off, your gauge is likely out of adjustment. I bought the diode for my alternator swap at RadioShack for about 2 bucks for a 2 pack. The package says 'Epoxy Rectifier Diodes' on it and the part number on the package is 276-1143. I'm not entirely sure if this is the diode that I should be using for the internally regulated alternator or not (haven't swapped alternators yet), but its rated at 3amps and 200PIV (whatever that is). Hope that helps. Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted February 11, 2004 Share Posted February 11, 2004 OK... so i'm testing this out... got a new battery, started the car today... the volt gague reads about 15.8 running, couldn't test at the battery as i was keeping it alive... anyway... i took off the hot lead after i turned it off (lead off the altn. that is) so we shall se what happens. -Ed Quote Link to comment Share on other sites More sharing options...
Muskrat Posted February 11, 2004 Author Share Posted February 11, 2004 I just got done talking to another Z guy I know that suggested a solution he found for his alternator problem. Check your fusible links, you may have connection problems there. Oh yeah, its alternator season, according to the guy at O'reilleys. Quote Link to comment Share on other sites More sharing options...
Guest mkokimoto Posted February 14, 2004 Share Posted February 14, 2004 I tried doing a search and couldn't find anything else more closely related to the problem I seem to be having. I re-wired my car recently, with an alternator from a 280z turbo, unused P connector, but the other two, sense and idiot light are hooked up. I took the alternator to autozone and tested fine. Sense - hooked to battery. energize - hooked to idiot light, then hooked to switched ignition source, per instructions on other posts. now when I start and run the car, the car reads about 14.5 But the idiot light stays on. Turn the headlights on, the idiot light stays on also. The car turns off okay, no diode needed because I suppose its because it runs an aftermarket ignition system. But the idiot light not working right is bothering me. I tried hooking that wire straight to the 12v ignition on, but the amount of current going thru the wire makes it hot to the touch. Right now, it charges fine even with the headlamps on or off, but that light stays on no matter what. Well, when the idle drops super low, the light turns off. Is this really how the alternator was supposed to be hooked up? So I have 4 wires on there the two on the t connector, sense and energize one that goes to the solenoid, carrying the amps one that goes to the body for ground. I'm hoping that im as clear as I can be, but I'm tired from a marathon re-wiring project since I dont have my own garage and had to borrow while the roomate was out of town. now im just going on thoughts here, but I think that this is a voltage feedback thingie. Pardon my lack of terms, but I'm beginning to think about the problem and if i install the diode, the voltage which is being pushed by the energized field, might be putting a higher voltage into the ignition circuit, causing a voltage difference which causes the light to light up? so if i install the diode, the voltage will only be able to feed one way, and not allow the field to feed voltage back thru to the idiot light? Quote Link to comment Share on other sites More sharing options...
Muskrat Posted February 14, 2004 Author Share Posted February 14, 2004 Have you tried driving your car around the block? If the idiot light is on just at idle, I wouldn't let it bother you... if it stays on though, you may have made a bad connection somewhere. I know I'm generalizing, but it's early (late?) and its snowing. I believe that you do have all of the connections that you listed installed correctly, however. The field wire should be plugged into a switched ignition source with the idiot light installed on the same circuit. This will supply current to the alternator (from what I've read) while the engine is revving up to speed during startup. Quote Link to comment Share on other sites More sharing options...
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