Alternator Short?

[Expando1]

Hi all, I have a 1998 Nissan Sentra with 215,000 miles. About a month ago the oil light and the battery light on the dash comes on at the same time when i rev the engine; when i hit 50mph it stays on constantly. I have no starting problems and no hesitancy with acceleration. I took it to autozone and they check the batter and alternator and told me both were fine but I have have a grounded wire somewhere that's the culprit. Does this sound right? If so, how do I find where this located?

[slideways...]

that sounds right.
look for damaged wires in the alternator harness, and through the fusebox, possibly into your dash guage cluster. check them with a voltmeter one connection at a time.
checking wiring is the worst part about working on a car.

keep in mind, autozone isnt omniscient, so be prepared if your alternator does happen to go out. its possible something is wrong with it that wouldnt show up on a in-car scanner.

also, if you want to do a very basic alternator test, put a voltmeter on the battery terminals. it should read 11-13 volts. start your car. the volts should go up to 13-15 V. rev the engine.

and the voltage should not go up as you rev. maybe a little, but if they go up alot, it means bad alternator.

also if the voltage doesnt change when you start the car, that means bad alternator.

also, if the volts go above approx 15.5V, that means bad alternator, but i dont think thats your problem.

otherwise check wires. bring lots of excedrin and jolt.

[Expando1]

Thanks for the tips, sideways. I didn't get a chance to do any of that yet but this is what happened this morning. I was driving to work on the freeway and as per usual the oil light and the battery lights were on simultaneously but otherwise the car started on the first attempt and the engine was running well.

I then noticed that the airbag light started to blink...so i thought, hmmm...interesting, this just may be a fusebox/wiring issue as sideways had said. Then within 2 minutes of the airbag light starting to flash the engine dies. I coast to the shoulder and try to start again but it seemed the battery was completely dead...i.e. no turnover, no clicks from the starter, no lights lit on the dash. After standing in the cold for a while, I got a jump start and it started perfectly. I tried to drive it back home and as has been happening the same two lights (batter and oil) were on. About 2 miles later, the speedometer drops to zero and i coast into a gas station's lot. As i sat there the engine was still running but it was sputtering along behaving as if it wanted to stall but then gets back to smooth idle for 30seconds before it rough idles again momentarily then smooths out...then it just stalls entirely.

I jump start it easily again but this time i figure that since i'm at a service station i'll just leave it there and have the mechanic look at it. It being sunday today the store clerk said he comes in later so he'll call when he's looked at it but off hand it sounded to him(the clerk) that it's the computer board, and they don't work on that at their shop.

i'm thinking alternator now...either alternator itself or a grounded wire as sideways mentioned that's wasting current preventing the battery from charging effectively. but bad battery, alternator, or computer board are in there. ok, so what do you guys think??

[slideways...]

replace the alternator. id be willing to bet that all your probs will go away

[Expando1]

well i got it back from the garage today with the alternator replaced. all the light are off now and things seem to be going well even at highway speeds. i bought a new battery at walmart and put it in anyway. when doing this i noticed that the terminal clamp on the positive pole was cracked vertically at the base and that someone had inserted a strip of foil on the pole underlying this crack...interesting. I bought new terminal clamps at walmart after i saw this but i can't for the life of me get the old one off the battery cable. perhaps a service shop will do it for me...i'm hoping for free since i already bought the part, but everyone seems to want to charge labor no matter how minor.