Zmon

iTrader: (2)

+1, that's how mine went with the light coming on first. Next morning, it really didn't want to start. Battery tested fine so I replaced the alternator. It was the original that got me to 165k, and I ended up buying a reman Denso from Amazon which I believe Denso remans those themselves (I wouldn't quote me on that though). My battery is barely a year old, and fortunately, the alternator didn't take it with it and it still tests fine.

Really not that bad to DIY if it comes to that, the problem is that nut on the back of the alternator that is a real PITA to reach and not drop. Reports around here are you can run around without it, I lost mine but ended up grabbing another one from the dealer anyways since it was only $1. One super pro-tip is to tape that nut onto your socket when you go to put it back. I would change the belt during this time as well if you've never changed it since you have to take it off anyways.

2013FSport

iTrader: (2)

More often than not there are no symptoms when the internal components fail. I say this as in, you're not going to get a weeks notice or even a days notice. More likely it will just quit. The only exception is that under load you notice the alternator has louder than normal whine and it's temperature is elevated. Both of those imply you're checking it and put your hands on it to notice it has a fever. But lets face it, we are not coddling our alternator until it's dead and being pulled so....

There are two main components to the alternator that die. The rectifier bridge of diodes that take the Alternating Current (AC) and convert it to Direct Current (DC) and the regulator that maintains the system voltage. Shock to the alternator is the number one killer. So lets say you leave the lights on one day and deplete the battery. You jump it but the leads are reversed. The bridge diodes for the most part can handle this, while the polarity sensitive regulator that is used to having DC only gets damaged. Not killed but damaged. Although it may survive today, it gets compromised. Then on a day when you load the system with all the accessories on, the current load causes thermal expansion and the components fail lighting up the dash and you're on the hook for a ride home. That said, diodes and regulators fail for no reason all the time but heat, age, and shock are the primary killers.

Look in this picture below, there are 12 rectifier diodes converting a sign wave of high voltage AC to DC, whereby the blackbox regulator keeps the voltage in check so the battery gets charged, the engine runs and the accessories work. Often times that smell people smell is one or more of those diodes short and the current from the stator burn them up cooking their bodies. In some cases they open up (not shorted) and the alternator continues to function but at a reduced current. In other cases they short, the new SMART cars detects "that ain't right" and the computer shuts down the rotors coils (that tiny loop at the bottom right in the picture) so the alternator no longer produces energy. That field rotor is an electro magnet. Apply DC current to it makes it a stronger magnet. The stronger the magnet, the higher the output from the alternators stator coils. No DC applied to the rotor and the alternator literally produces no output. In short an alternator needs 9+ volts to wake it up and make it work.



BATTERY CHARGING: A lead acid battery in good health is >2.1volts for per cell or 12.6 volts. Typically at 70F, about 12.85 volts is pretty normal for fully charged at rest, no load. Current charges a battery not voltage. To charge a 12.85v battery it needs voltage greater than 12.85 volts for current to flow. So lets say it's at 12.85v, to maintain loss pretty much anything in the 13 to 13.85v range is adequate. Voltages Rise quickly to 14'ish after starting as it charging the battery after being depleted. That said we do not want to see sustained 14.4+ voltages as this will boil the battery dry.

Folks; as a reminder, I renewed my year long subscription to www.alldatadiy.com for $15 last night. I posted a thread last year on the topic and the promo code was YEAREND18, try YEAREND19. The cost was like $13 a year. Bingo --> DIY repair info site, ALLDATADIY.COM $13, 12mo

LexStylez

Had my alternator replaced recently at 88,000 miles. Didn't get any battery warning light like some people are getting. While driving and making a turn, I lost power steering. Opened the hood, smelled like burnt plastic and the headlights were flickering. One of the symptoms of the alternator going out is a whining noise. I didn't know and thought maybe because of the cold weather it was making whining noise. If you have that symptom, get it replaced ASAP because you don't want to be driving on the highway and all of a sudden lose power steering.

lexus-is2

Sounds really scary if it was to die on the highway. If it dies on the highway, does the steering still work just becomes hard? I'm going to do the digital multimeter test tomorrow. I've also purchased one of those cheap battery and alternator testers pictured below so will try that out. But as @2013FSport said most often there are no symptoms and they just die. It could test fine but then still die This is quite worrying. It's not a cheap part, would you recommend I just change it to be safe or wait?

2013FSport

iTrader: (2)

At speed you can steer it, there just won't be any mechanical assistance. Of all of the electrical loads on the system, short of the battery itself the power steering is the single largest load.

Anyone driving and thinking something is wrong with the charging system TURN OFF EVERYTHING you don't absolutely have to have!, like butt heaters or A/C, heat, rear defrost, fog lights, radio, etc. go from headlights on to OFF and hazards ON if that means getting off the interstate. Even minimize brake use if possible.

Not that I recommend this but....
I drove home 30 mi in the cold after disconnecting all right side lights, pulling fuses for ABS, EPS, and other crap I deemed high power draw that I could not disable in the with a switch when the alternator died on another vehicle.
In the end, the battery was so dead it would kill the engine from lighting one 1157 bulb via the brake pedal. But I didn't walk in 20°F cold! Battery lived too as I charged it when home.

lexus-is2

So is it worth changing it even if it's not broken at the moment or wait until it does? What would you all do? It could be that it's on its last leg or it could be that it's still healthy and can give plenty more miles. Wondering if the climate has anything to do with it dying at a certain time? Has the failed ones died in cold or hot weather or both?

mandyfig

Batteries die when temps go down, if the battery is on its way out.

2013FSport

iTrader: (2)

If it were a 1995 Camry I'd change it at 325,xxx miles. These however, just don't seem as robust. Based upon your level of assurance that car needs to be as reliable as possible, and to reduce stress, you might just plan on doing it now. Unfortunately you will never know how long it can last. Even a new one.

Shaq8001

I have a 2007 Lexus is250 RWD when driving on my way home the battery light the VSC ,ABS ,Brake light come on ( Check VSC) illuminates and the car starts to hestiate when accelerating and power steering get hard . I replaced the alternator with a reman one the charging voltage is 13.4V and the battery light on still and when in drive does response but reverse fine code C1241 and B2416.

MikeFig82

iTrader: (13)

Get your battery load tested at the auto parts store.
Make sure all your connections to the alternator are secured properly. If you look at your battery, and it doesn't have the cover on. Check for battery bulging maybe your old alternator was overcharging? JM2C to things to look over briefly.