Dash lights on, alternator voltage too high, dead batteries, etc. help please!

[Mister 26]

I posted this in the Infiniti online mechanic section, but I'm not sure if it's more appropriate here or there, so this is a repost. If an admin will kindly decide for me and delete the inappropriate one, I'd be thankful.

I have a 2001 Infiniti I30T that has been having some problems lately. My very first symptom was a jerky steering wheel, as if the power steering was going on me, accompanied by a high pitched electric motor sound (this sound is new and has not gone away). I checked the power steering fluid and it was fine, so along I went. The next symptom I had was while driving home one night - headlights seeming not bright enough, then the dashboard lit up like a Christmas tree, and then no power. Dead battery, seemingly caused by a bad alternator. Installed a new battery and tested the voltage from the alternator and read 16. At the time I did not know this is too high. Live and learn.... Off I went again, but now the battery and brake dash lights were on. I thought this might be because the computer needed some time to reset. I was wrong. More Christmas light displays ensued, and I was stranded again. This time I took a tow straight to the mechanic where I was informed my alternator was bad. Several less Christmas presents later off I went with my new alternator. All was good for three days until I once again felt the power steering stumble, and sure enough the dash battery and brake lights were back on. Another tow to the mechanics followed, where another alternator was installed. That very night the same lights were on again but then they went off as I tried to limp the car home. Now when I start the car the lights are on but then they go off. The voltage out of the alternator is 18!!! I'm afraid to drive to the dealership to see if they can help for fear of another towing bill.

Cliffs:Over the last week I've been thru 2 alternators and a new battery.Battery and brake dash lights are appearing intermittently.Voltage from the regulator is too high.

Any ideas what is wrong here?

[loystock]

There is probably nothing wrong with your alternator. Most likely it is the sensing line that's 'open.' The old battery died probably due to overcharging. Your new battery may also die unless you correct the problem - 16/18VDC is just too much. Other electrical components and controllers in your car may also get 'fried' if this condition persisted.

The alternator has an internal voltage regulator (VR) that limits the charging voltage to 14.1 to 14.7 VDC, assuming normal electrical load. The sensing line from the battery is thru terminal 'S' on the alternator. Anything more than 15VDC indicates a problem with the alternator or the sensing line.

Check the Fuse #70 (10A) in the Fusible Link box besides the battery. That fuse provides the 'S' (sense) input to the alternator. If the fuse or that line is open, the IC in the Voltage Regulator can go 'crazy' since it doesn't know the battery voltage and will try to raise the charging voltage. You might as well check the condition of the main fusible link, 120A.

As for the alternators removed from the car, have then checked at AutoZone. Both of them are probably good..

[Mister 26]

There is probably nothing wrong with your alternator. Most likely it is the sensing line that's 'open.' The old battery died probably due to overcharging. Your new battery may also die unless you correct the problem - 16/18VDC is just too much. Other electrical components and controllers in your car may also get 'fried' if this condition persisted.

The alternator has an internal voltage regulator (VR) that limits the charging voltage to 14.1 to 14.7 VDC, assuming normal electrical load. The sensing line from the battery is thru terminal 'S' on the alternator. Anything more than 15VDC indicates a problem with the alternator or the sensing line.

Check the Fuse #70 (10A) in the Fusible Link box besides the battery. That fuse provides the 'S' (sense) input to the alternator. If the fuse or that line is open, the IC in the Voltage Regulator can go 'crazy' since it doesn't know the battery voltage and will try to raise the charging voltage. You might as well check the condition of the main fusible link, 120A.

As for the alternators removed from the car, have then checked at AutoZone. Both of them are probably good..

Thank you for the response. The car went to a Nissan Dealership this morning (there are no Infiniti dealerships anywhere near me). They've worked on this car before, replacing the o2 sensors and cats. At this point they're just doing diagnostics. I'll ask about the fuse and fusable link.