well it was working fine (to my knowledge) and recently it started freaking out. sometimes when i turn the key to the "on" position the battery light lights up and others times it doesn't. it is my understanding that this is how you know the alternator is getting the "start charging junk" signal. but after some testing with a volt meter i found that despite if the battery light turns on it will not charge properly. not only this but smoetimes it DOES charge properly. its very finiky and it has left me on the side of the road more than once now but when i go to get it checked out as i can't figure it out, it works jsut fine. driving me crazy. i have noticed that sometimes when it actually does charge that it will do it at 13.2 volts and other times it will go at 14.2 or so. i took that with a "charging is charging" attitude which now i am thinking isn't right haha

is it the alternator? bad voltage regulator(which if it is i believe is in the alternator anyway-right)? bad connections somewhere - the wiring harness to the alternator is snug and not to brittle despite being an old car (91 NA 2 seater)

 

yes, the voltage regulator is internal on these cars. I would recommend just changing your alternator. IF it's leaving you stranded, it couldn't hurt. It's weird that it's erratic like that. Go buy one from your local auto parts store with a warranty and change it yourself, not a hard job to do, just a little cramped.

 

Because the problem seems to come and go, it sounds like it could be a bad connection. The car I just got has a dead spot in the positive cable (I found out the hard way) and from wiggling it around is how I found it. It could be the same problem for you. It is also possible that the Alternator itself is begining to fail... Either a bad diode or regulator. From what I can tell, replacing the alternator on this car is about the only repair that doesn't require 3 hands and an engineering degree . Check the cables and connections really good before you condem the alternator. If the cables and connections are good, I say do what Emo said and replace the alternator. Rod.

 

2nd on what Rod said.......... especially if it's intermittent.

I'll add....... I had a vehicle where the charge light on the dash came on. Car had 1xx,xxx miles on it. Figured it finally needed a new alt. As I was removing the alt., I noticed corrosion at the connection, cleaned the connection, reassembled, alt. worked fine till the car went to the junkyard at around 270,000 miles.

 

where are the cables though from the switch that tells the alternator to turn on? i have no idea how alternator wiring works, as far as i know its two wires, ground and then a positive. and rplacing the alternator isn't that hard you say, all the shops tell me its way hard and way expensive. i am a good mechanic and in fact have an engineering degree i gues i don't want to think its a bad alternator as it works... sometimes.. thats jsut weird to me, could be loose or dirty connections but again the way it works is weird sometmies it does work, other times it doesn't. it could be working this time i start it up, but i will park it, come back and it will work this time.. i don't get it. i will check the connections first then i will do the last resort and change the alternator i suppose

 

is there a write up on changing the alternator?

 

here you go:
http://twinturbo.net/net/viewmsg.asp...&msg_id=929376
I think I'm going to have to make a link page as well someday! I'm always posting these!

 

Any mechanic that's telling you replacing the alternator is "way hard and expensive" are full of horsesh!t and are setting you up for a fisting. Put er' on a rack, lift it up, remove the skidplate and dump the alternator. At least thats how my mechanic has described it and he's put in 3 for me. 1 replaced the original, a second one replace the WRONG one they put in (too small, car killed it) and 3rd time to replace the last one that was murdered by steering fluid dripping on it.

All in all about 300 bucks if you buy a brand new one and have it shipped from Nissan APAC witha couple hours labor involved but most likely they will have a nice rebuilt one ready to go which essentially IS a new one in an old housing.

 

This is the same problem I have. The power loss is intermitent. I've also check the voltage when the car is running and it reads 14V but when I turn it off and check the battery voltage again it starts to go down to 11-10-9v until finally the batery died. I took the alternator out and had it check by Autozone and Pepboys. The alternator is OK!!. There is definately a parasitic power loss that I can't find. It is really hard to find the source of the power drain. I've check the continuity of the wire coming from the battery to the alternator and everything is Ok. Th eoly way I can truly diagnose and solve this problem is to change my harness and some of the old wiring when I remove my engine for a turbo upgrade.

 

Those basic tests that PepBoy's and The other Auto Parts chains do, do not test for proper Diode function. They can only tell you if the alternator has the ability to charge. I found this out the hard way. A bad diode will exhibit the same parasitic power loss symptom that you describe. In other words, it's quite possible that you do in fact have an alternator problem... Sorry. ... ... ... ... Rod.

 

What you need to do first is run the motor, then with motor still running, disconnect the battery cable, and check to see if the battery voltage is still dropping. If it is, then the battery is no good.

 

i thought this was a nono as the battery keeps the alternator voltage restricted to yay many volts and removing it allwos the alternator to pump out 1,278,895.6 volts and fry everything

 

The regulator regulates the output of the alternator. I've heard of the myth that you describe. If that was the case then you could also fry the electrical system by jump starting another car with a dead battery. I have never heard of any actual problems from doing this. I've done it many times.

If you have any reservations about it, just take your battery and have it tested. Unless you tell me that you have a newer battery, I'd say that it is the first thing to check. Especially by the problems that you describe.