The alternator on my 94 maxima won't work on my car. After I found this morning that the battery lamp was lit, I checked the voltage tonight. There is no difference of the voltage when car is runing or not, that is 12 V. I took the alternator to the store from where I bought the alternator, It was checked and the voltage was ok. However, after I installed the alternator, the voltage is still the same, 12V even on the alternator side (without connected to the alternator, the two disconnected cables showed 12 V.) Is the alternator dead or not? I going to have it checked in another store tomorrow.
Your help is appreciated.

 

check your fusible links

 

I tried, but I couldnot find any thing that says alternator. Thanks for your help.

 

do you have a VE or a VG? the charging systems are different

 

It is VG, not a VE.

 

yeah, so based on the wiring diagram, check the gray fusible link, and the green one. I don't precisely know which ones, but honestly, just look thru the little viewer window of all of them because none of them should be broken. also check the fuses that relate to it.

 

specifically, inside your car, the 8th fuse down on the left, and the 7th on the right. but unless you have a lot of things not working, I don't either of those fuses, because those two have about 10 systems each to handle... so it's more likely fusible links or the harness.

 

I checked the fusible link fuses, they are fine. What is the harness. By the way, I checked the voltage on the alternator when the car is running, the voltage is the same as the battery, what doesn't this indicate?
Thanks capedcadaver for your help.

 

'harness' is the general description of the wire connectors that are conneced to devices. so the connector on, say, your headlight... the connector on the headlight is "terminal side" and the wires from the car are the "harness side". all the big huge wire packs are part of some harness or another.



^^^connectors E17 and E18 are the alternator's harness connections^^^

 

Stupid and obvious question I know ..........

Is the alternator getting spinned by the engine? (belt there and tight?)

If the shop tested the alternator ok in front of you while out of the car, I would take the whole car with alternator fitted back to the same store and have them test it in the car.

From what you are describing (alt light on in the dash and measuring only batt voltage on the alt) you must have a funky alt (if the alt is rotating)

 

i dunno. for whatever reason i'm still drawn to think there's a wiring problem... like an unseated terminal in one of the connectors or something, or a bad connector or corrosion or.. something. I mean all it takes is one bum wire...

 

I forgot to mention that the brake light is also on, and off sometimes, but the brightness is only half of normal, so is the battery light in brightness. Besides the positive and ground wires, what are the other two wires? Do they control the alternator? In other words, if the alternator is good, it should outpot 14 V anyway even if the connectors are not good?

 

i've been looking at this:


that should show the 4 wires you're talking about. i'll look at it more closely to try and see exactly what they do.

 

I doubt it because in the case of a modern alternator things are really simple - if its properly fitted mechanically, then it requires only the battery to be connected (in this case it obviously is because 12V is measured on the alt output) and the alt light via the instrument cluster must supply initial stator current (which it is in this case because the alt light does turn on).

If only those 2 requirements are met, then if the alternator is present and spinning, everything else is happening inside the alternator (under control of the built-in voltage regulator) - irrespective of any other wiring on the car - it must and will produce 14V on the alt output terminal if the regulator/stator/rotor are all working as they should - if any wiring after that is funky, then sure you may have a batt charging problem etc, but your goal must be initially to get around 14V on the alt output terminal else you are wasting your time

 

so then if the light is lighting up, then the alternator must be hooked up? and if you disconnect the alternator the light cannot possibly light up? I was just thinking that maybe the alternator-to-battery connection was interrupted somwhere, but that the low-battery signal came from the battery regardless of alternator

 

Correct - whether the current flowing through that pilot light to the alternator actually energizes the stator/rotor is a function of the integrity of the electronics (voltage regulator and 9 diodes) inside the alternator (as well as the coils, brushes etc etc inside the alt itself.)

In a modern alt, you can actually remove the batt from the alt altogether and the alt should still be able to generate 14V on the output terminal as long as its spinning and the pilot light is connected and working - irrespective of load on the alt (its a bad idea to do this because huge surges can often be setup inside the voltage regulator where electronics may not be able to cope with the spiky nature of the output of the alt under those conditions - the batt serves as a kind of "filter" to the voltage regulator)No - its not telling you anything about the actual battery level.

The pilot light on the dash is telling you the alternator output voltage is lower than the battery voltage (ie the alt is not charging the battery) - the alternator's initial magnetizing current is supplied by that pilot light through a diode to the brushes - once the alternator starts producing current, the diode inside the alternator gets reverse biased causing the pilot light to turn off - ie - the alternator use the current that flows through that light to get the process of generating current going.

 

that's what I gathered from the wiring diagram but then I was like "no.. that can't be..." but now it makes sense. if the signals are the same, wiether 1v and 1v or 100v and 100v, the difference between them is what will cause electrons to flow from one side of the little light to the other, and the bigger the difference the brighter the glow.

i love diodes. i really do. they come on very handy, like, for my little corner light mod..

 

Diodes are indeed modern man's best friend.

 

this is really dumb, probably dangerous, unless youre confident in your skills of working with cars.... get your car started, and after it is started unhook the battery.... if the alt is good the car should run fine without the battery connected... just some insight

 

vvv that was already addressed vvv

 

I did that to disconnect the negative. The car stopped instantly.

 

I have the alternator checked by them(advanced auto parts) again, and it turned out that the alternator is dead, so I got an one-time replacement under the warranty. However, I will not shop with them anymore considering the hassle I got.

 

Did you happen to get the alternator from Autozone? Cause this is the same issue I am going through right now where it worked then didnt then did and not it is dead. On the output of the alternator I am getting .5 volts.

 

You should never disconnect the battery while the engine is running, that alone can be enough to destroy a perfectly good alternator. In addition, there will ALWAYS be battery voltage (12v if the battery has a good charge) at the output of the alternator, because the alternator connects directly to the battery positive terminal. The ONLY time you will not see battery voltage at the alternator output is if you have managed to cook a fusible link.

Most alternators have 3 main connections. One is ground (sometimes through the case, sometimes a wire in the harness). One is constant 12v. This is the charge lead. The final connection is a switched 12v which starts the alternator, and provides voltage feedback to the regulator. This should be 0 volts with the key off, and battery voltage with the key on. All three of these connections must be intact for the alternator to work. If all connections are clean, and tight, and proper voltage (or ground) is available on each, then a voltage measurement of less than 14v with the engine running will indicate a bad alternator (assuming that the belt is in place, and properly tensioned).