In my on-going effort to get to the bottom of my repeated battery failures (see earlier post) I am now using a voltmeter to monitor my alternator and battery. It seems that I am getting 13.5-13.8 from the alternator when the car is cruising at 50-60mph but it drops down to about 12.5 when idling in drive. Shifting to neutral will increase the voltage output back above 13.
What is this telling me?

Thanks

 

12.6v is required to charge the battery and keep things running. While in drive and stopped the RPMs drop a little explaining the drop in voltage as the alternator is not spinning as high.
Is anything else on such a ac, lights,etc while checking? The voltage regulator will only go so far while your car is idling.
If you load up the entire car, fogs, lights, ac, blower motor, stereo, etc while at idle you will most likely see the voltage drop even further which will then be depleting your battery. This is not SC430 specific as it is very rare that someone will sit idle with everything on the car going full blast.

 

Thanks. Only the blower motor was on, but was high. I'll check the output a little closer. May have droped to 12.3 for a moment.

 

With the engine off, the voltage at the battery should be about 12.5 to 12.8.

The voltage at the battery with engine idling and again with the engine at about 1500 RPM should be the about the same (about 13.6 to 14.2) if the alternator, battery and cables are good. This is the voltage level set by the voltage regulator.

Your numbers sound like the alternator is producing sufficient volts such that it would not be cause of battery to failure.

 

2.1 volts per cell. 6 cells in a 12v battery. Anything lower and the battery is not getting charged.

 

It would take a lot of idling at .1 volt under to drain a battery!! I think you'd run out of gas first.

 

It is not a matter of that versus his question on whether his system is operating as it should or not. Numbers can also be off by the scope being used.

 

Are SC's known for alternator problems. I just recently got one, my car went dead, I replaced the battery. Next day still went dead, figured out alternator is gone. Where would be a good place to get another one and how much can I expect to pay for one? Should I get a remanufactured one, are they reliable?

 

Nothing wrong with remans if done correctly. But to answer your question, a few reports have come up but for the most part pretty reliable. Shoot, had a good working used unit I recently tossed in the trash.

 

Oh man, are you serious! Darn it...anyways. So I could get a reman and shouldnt go out on me in about 3 years...thats how long ill proly have the car.

 

Never any guarantees, but you should be fine. If a local rebuilder is going to do it, ensure they have use the correct amperage regulator. Perhaps they will even go with a higher unit.

 

Is it worth $500 to get a brand new one installed by a Lexus Professional including labor?

 

That is completely up to you. A Lexus Professional? Seen a few of them. A few I would trust, others I would not want replacing my wipers.

 

I guess meaning at the dealership...they said labor would be $100 for an hour and the alternator costs roughly $400 brand new. I guess I dont have a cheaper option so Ill have to go with it.

 

check sewell first. their parts are often cheaper than your local dealer. at one point, i thought i needed to replace my center console and my local dealer quoted double sewell for the same part. that said, my local dealer is a bunch of crooks. but it doesn't hurt to check.