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Discussion Starter #21
I'm just wondering why the regular test failed. I'll test the diodes and ripples.
Yea, their test doesn't make much sense unless it's detects a ripple.voltage, but I don't recall them being able to test that. Only charging voltage. I would take a 30 minute drive and retest maybe at NAPA or a place where they are knowledgeable.
 

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I don't know what type of test they run and how it works but I figured out my problem.

Before I went in for the test, I disconnected the regulator and I noticed there was a lot of white crusty stuff inside the socket. I just plugged the regulator back in and pushed it in a bit and the car passed the test. The battery now charges to 100% @ 12.75v.

I'm going to remove the regulator plug again today and put some dielectric grease in there to prevent corrosion.

The funny thing is, I actually pressed the regulator plug in a bit more before but it still failed. I guess when I unplug and plug it back in I wiped a bit of the crusty white stuff off and there's a good connection again.
 

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Discussion Starter #23
I don't know what type of test they run and how it works but I figured out my problem.

Before I went in for the test, I disconnected the regulator and I noticed there was a lot of white crusty stuff inside the socket. I just plugged the regulator back in and pushed it in a bit and the car passed the test. The battery now charges to 100% @ 12.75v.

I'm going to remove the regulator plug again today and put some dielectric grease in there to prevent corrosion.

The funny thing is, I actually pressed the regulator plug in a bit more before but it still failed. I guess when I unplug and plug it back in I wiped a bit of the crusty white stuff off and there's a good connection again.

Are you talking about the 3 wire harness, mentioned in the DIY that hooks up to the alt? If so(which I think you are), good find! Luckily you found it before the alt's regulator went bad. That's not only the regulator but also the stator winding feed and feedback. The regulator is internal and the B+ stud is it's output. There definitely should be some dielectric grease on that plug and it should be tight. There's also a cover on the battery bolted connection on the stud. You should be good after a nice cleaning. Use some electronic contact cleaner and grease.
 

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Yep the 3-pin connector to the regulator. When I look down into the socket I can see there's some gunk in there. I just put on some dielectric grease into the socket (on the wire connector, not alternator socket) and gave it a good insert. I'm going to stop by Autozone on the way to work to have them test it one last time to make sure I have a good connection.

I tested the regulator with a multimeter and it seems like it's doing its job. Reving to 2-3k got me a max charge output of 13.96v while being idle was 13.93v. Thanks for the troubleshooting help!
 

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Question on the 3 plug wire: the feed to the ecu, should there be a reference voltage when the alternator is properly operating or not voltage when properly operating? I had my alternator test on a bench and it came out fine but I am still getting a battery light. So I wanted to test out that ecu reference to rule out whether the my ecu went bad or the alternator.
 

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Question on the 3 plug wire: the feed to the ecu, should there be a reference voltage when the alternator is properly operating or not voltage when properly operating? I had my alternator test on a bench and it came out fine but I am still getting a battery light. So I wanted to test out that ecu reference to rule out whether the my ecu went bad or the alternator.
Good question and I've looked into it alittle bit, but without verifying myself yet. According to the FSM service hints:
(B) 1-Ground: Below 1.5 volts. with ignition switch set at ON position and engine not running.
Nothing else is mentioned, nice. It would be good to find out what kind of signal that is putting into the ECU. Providing your 10A Gauge feed(IG) is good as well as the 7.5A Stator fuses, i wonder if that produces charging voltage to ground(so verify the alt really is putting out 13.2-14.8 at the battery while running in the car). It appears the feed from the 10A Guage has more to do with the battery charge light than the L signal to the ECU. Make sure you have a Gauge terminal connection(red/blue). If you lost any of those two fuses, you would get a light but the shop would read it as a good alt.
 

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I'm having what I think is an alternator issue with my 2001 is300...

First noticed it a few days ago when pulling away from a light, suddenly the voltage just dropped and all of my gauges turned off and came back on. Then when I was leaving work that same day I had everything turn off while leaving the parking garage, this time the engine shut off and I wasn't able to immediately start the car back up. The next morning I had some trouble starting the engine, it would turn over once and then all of the gauges and clock faded out. Eventually I was able to get it started but decided to take my RX350 to avoid the chance of being stuck in traffic.

I think there was a whirring noise like the alternator drive belt was slipping when things died. Will try to pick up a new serpentine belt on the way home today, already have a spare alternator to try.

Anyways I'll check my alternator and battery tonight, thank you for the how to!
 

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Discussion Starter #29
I'm having what I think is an alternator issue with my 2001 is300...

First noticed it a few days ago when pulling away from a light, suddenly the voltage just dropped and all of my gauges turned off and came back on. Then when I was leaving work that same day I had everything turn off while leaving the parking garage, this time the engine shut off and I wasn't able to immediately start the car back up. The next morning I had some trouble starting the engine, it would turn over once and then all of the gauges and clock faded out. Eventually I was able to get it started but decided to take my RX350 to avoid the chance of being stuck in traffic.

I think there was a whirring noise like the alternator drive belt was slipping when things died. Will try to pick up a new serpentine belt on the way home today, already have a spare alternator to try.

Anyways I'll check my alternator and battery tonight, thank you for the how to!
I can almost guarantee your problem is the belt because accelerating from a stop your drive belt is slipping which WILL cause a brief loss of power. Normally the alt produces very little power at idle so for you to lose power as alt rpms go up tell me the alt is not spinning right. Also, besides the obvious cracks and old age, i recommend changing the belt every 30k-40k miles.
Now your issue could also be a bad spring tensioner. Take your thumb and index finger and try to turn the belt 180 degrees. It should be difficult to do so. It's pretty rare to kill our Denso alts because they are built well, remember whatever you do, do not disconnect the battery while the car is running. If it's not the belt or tensioner post back.
 

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I bought the car with 50,000 miles and now have about 155,000 miles and have not changed the belt yet, guessing it's a bit overdue. Will check things out a bit more tonight and post back when I have more information.

Thanks for the help and quick reply.
 

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Hey Jason, car battery died on me yesterday(started noticing weak cranks 3 days prior). I jumped it off and was reading 13.54V running, drove home with no issues, when I left it alone for about 2 hrs and came back to check it with the car off and the battery was at 10.28V which leads me to believe its the battery since the voltage drain was unusually quick and possibly a cell went bad. When I get off work today I will check ground connections and try to do alternator checks as well. That battery had been in the car since before I purchased it 3 years ago so it maybe time for a replacement.

I called around to a few dealerships to get a price quote on a battery since the TrueStart has a 84 month warranty for the same price as a Duralast and I was wondering is the 28800 part # for Lexus superceded by Toyota part # 00544-24060-575 (which is the same battery for a Scion TC oddly enough) since the 28800 isn't sold by the dealer anymore for Group 24?
 

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Discussion Starter #32 (Edited)
Hey Jason, car battery died on me yesterday(started noticing weak cranks 3 days prior). I jumped it off and was reading 13.54V running, drove home with no issues, when I left it alone for about 2 hrs and came back to check it with the car off and the battery was at 10.28V which leads me to believe its the battery since the voltage drain was unusually quick and possibly a cell went bad. When I get off work today I will check ground connections and try to do alternator checks as well. That battery had been in the car since before I purchased it 3 years ago so it maybe time for a replacement.

I called around to a few dealerships to get a price quote on a battery since the TrueStart has a 84 month warranty for the same price as a Duralast and I was wondering is the 28800 part # for Lexus superceded by Toyota part # 00544-24060-575 (which is the same battery for a Scion TC oddly enough) since the 28800 isn't sold by the dealer anymore for Group 24?
Hey Jim, it sounds like your charging system is doing it's job and either you have a battery that's near the end of it's life or possibly has an open/shorted cell OR you may have a high car-off parasitic draw. Obviously I would do a free battery check as you mentioned and go from there. If the battery is ok or if you want to verify your car isn't the problem then I'd do the parasitic draw test. I know my battery sits around 12.8vdc off and when the car is running at operating temperature the voltage is about 13.5vdc, so that looks good.

As far as OE battery part numbers, ToyoDIY is telling me the battery has the following PN's for Lexus and 00544-24060-575 is in fact Toyota's updated battery PN(used on actually quite a number of makes and models).
28800 BATTERY
28800-46120 80D26R-MF
28800-54232 80D26R

http://www.toyotapartszone.com/oem/toyota~truestart~battery~00544-24060-575.html
Hope this helps...lemme know how it works out. Hopefully it's just a bad battery, 3-4 years is really not too bad of a lifespan for modern batteries.

Edit; found some good info on various batteries and their applications. The battery you mentioned does have a BCI rating of 24.
http://db.tt/P46fHuXQ(from my dropbox)
 

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Discussion Starter #34
Ok thanks man. Will Do! :)
No problem bud, let us know it works out. If your battery tests OK, then I'd do the parasitic draw test on page 1, or you can do the test so you know for sure it's not an additional problem(Harbor Freights $5 meter works just fine in case you don't have one). Mine reads about 37mA after 5 minutes.
 

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No problem bud, let us know it works out. If your battery tests OK, then I'd do the parasitic draw test on page 1, or you can do the test so you know for sure it's not an additional problem(Harbor Freights $5 meter works just fine in case you don't have one). Mine reads about 37mA after 5 minutes.

Well that Duralast Gold that was in the car was manufactured 9/08 so that battery had done its job. 5 years is about right. I'm heading to the Toyota Dealer after work to get the TrueStart. :)
 

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I know this hasn't been updated in over a year. But, I just found this article and have read through this. I'm at work, not in front of the car at the moment. Issue started about 2 months ago, I have a 2001 IS300. The car has always started for me and has never given me grief. So I went to start it in November and the car wouldn't start. It was like the battery was dead. So i bought a new battery and changed it, because the battery in it was old, but the car wouldn't start. I diagnosed the issue and determined it to need a starter(not a tech!!!) I replaced the starter and the car still wouldn't start. So my technician brother determined the positive cable was bad, we replaced it and the car started. I was happy. I was able to restart it multiple times and drive it home. Where I parked it and periodically was able to start it no problem. So on Sunday I went to start it and nothing, no big deal it has sat in the very cold for over 2 weeks approx. I jumped it and it fired right up. I let it run for 20 minutes and shut if off, went to restart it and it wouldn't restart. Any ideas or starting points? Thank you
 

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Sounds like your battery is dead and needs a full charge, either that or you have picked up a slow electrical drain. 20 minutes at idle is not sufficient for putting any serious power in the battery, try a smart charger.
 

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Hi Jason, really found your post about charge/alternator/battery troubleshooting helpful from back in '09
got an 07 is350 which had starting issues and flickering and intermittent power (electrical) outings. Changed battery to new and after a few days same issues started occurring.
the cold sitting car reading fluctuates between 12.5 to 13.2, when started up it fluctuates as well and lights flicker. I kept the meter on the terminals and ran another wire from one of the grounds to the battery terminal where the readings jump to a proper 13.8. Wonder if you had any insights of what could be causing this and any remedies?

Best,
Paul
 

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Hi Jason, really found your post about charge/alternator/battery troubleshooting helpful from back in '09
got an 07 is350 which had starting issues and flickering and intermittent power (electrical) outings. Changed battery to new and after a few days same issues started occurring.
the cold sitting car reading fluctuates between 12.5 to 13.2, when started up it fluctuates as well and lights flicker. I kept the meter on the terminals and ran another wire from one of the grounds to the battery terminal where the readings jump to a proper 13.8. Wonder if you had any insights of what could be causing this and any remedies?

Best,
Paul
It sounds like you have an issue with your main ground cable. Not sure about the second gen, but on the IS300 the battery negative grounds to the body and then to the engine block. If you have an ohmmeter, I'd see what resistance you have from the negative battery post to the body and engine block(should be less than 1 ohm). It could also be your negative battery terminal connector if you placed the jumper on the actual battery negative post verses where the negative wire bolts up to the battery terminal. I wonder if it's just a loose/corroded battery terminal, but that depends on where you physically placed your ground jumper.
 

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Sure enough it was indeed the negative connector! After a dealer had fiddled with it for two hours and wanted a 'commitment' from me for more hours to take apart the dash I knew these monkeys wouldn't be able to fix anything except a fatter invoice bill. What's worse, the tech said he checked the grounds along the battery!
My pops and I decided to check again and after lifting the battery the negative was completely loose and corrosion made the bolt loose where the connection arced the bolt further loosened the connection.
Easy fix to simply tap in a larger bolt and secure the connection. Car runs like new.
 
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