Hi all, hopin to get some advice on my 2002. I recently replaced the battery and alternator after being stranded on the side of the road. I drove it a good couple hundred miles with the new battery and alternator over a few weeks with no issues.

Then after a little while I take it for a drive, all is looking good, then the dreaded charge system light comes on the dashboard, the instrument cluster starts going haywire, the engine is kicking and sputtering and then its dead.

I have replaced the alternator twice, thinking the first one was just a faulty part that I ordered, however, it's still giving me the exact same issue. I was able to jump start it and kept it at ~2000 rpms which I believe charged the battery just enough for me to get home where it now sits.

Anyone have any clue what's going on here? Any help would be greatly appreciated

 

Batteries and alternators tend to fail together because either one failing on its own will overload the other. But if you replaced the battery and the alternator at the same time, and they still failed, then either 1) one of the replacements was bad, or 2) something else in the system was broken.

Here are some diagnostic tests from the service manual in case they are helpful.

Edit: sorry this is from my 2004 manual, not sure if anything is different for your 2002 but I would try to find a 2002 manual...

 

what brand and where did you get your alternator? I replaced mine back in early summer this year (with part from Lexus). No issue

 

I bought one from advance auto parts that was remanufactured in mexico, I forget which brand specifically

 

That's your problem and it will keep happening until you buy a Denso remanufactured alternator.

 

OEM new alternator is only $190.

https://parts.belllexusnorthscottsda...060-50280.html

I bet you've already spent more than that in wasted time and labor

 

You need to find out if the alternator is putting out the correct amount of power? Or if the power is not getting back to the battery. You could have a corroded battery cable or ground wire that is your problem. You need to get the battery fully charged, either hook up a battery charger to it or take it to an AutoZone or whatever and ask them to charge it for you. Once it’s charged and reinstalled get your multimeter and check the Voltage on the alternator output, while the engine is running you should get around 14V if you aren’t then you have a problem with the alternator. Either it’s bad, or maybe the belt is slipping or something? If it’s got good voltage then check the + terminal on the battery and it should be close to what the alternator is putting out. If the voltage is low then you should look to replace the alternator cable that runs to the battery if the voltage is good then you want to look at a bad ground. I would get a set of jumper cables and connect one side to the battery and then the other positive should go to the alternator output and then ground should go to the engine block. Once the jumper cables are connected like this, redo the multimeter test and confirm that the voltage is correct at the battery and then replace whatever is your problem.

 

Thank you very much for the helpful tips, I will definitely try this before buying a new alternator

 

Some rebuilt things from autoparts stores will work decently (i always have had great luck with power steering pumps) but alternators from them are always just garbage.

Most of them seem to only last a few months if even that, and I have had many that were totally dead out of the box. Years ago, i had a "rebuilt" one from oreilly's that i put in a customers vehicle that was putting out almost 19.5 volts, which the car didn't like one bit.

As LeX2k said, find Denso branded rebuilt one. It'll be of good quality.

 

Agreed.
I go to local auto part stores to get parts for my Ford Taurus, not my Lexus.

 

So I took it for a drive for about 10 miles after cleaning the battery terminals and connectors with steel wool as it had a lot of corrosion on the connectors, and it had no issues. However, when I got back home I let it idle for a little bit while I tested voltage at the battery.

when I first parked I was getting 13.97 volts at idle, but it eventually dropped down to 11.6 and continued dropping when I had the fog lights and high beams on.

 

Since replaced twice look more at plug to alternator for bad connection. Your voltage check is indicative of a bad alternator or connections.

 

I actually spliced in a new plug the second time I replaced the alternator since it disintegrated on me when I tried plugging it back in. Heat shrink wrapped and all

 

When voltage lower put multimeter lead on center top of battery post first and then on battery connector. Put a jumper cable 1 lead at alternator as extension just to measure voltage there. All 3 measurements should be the same. Did you order from same source for both? Could be they had a bad batch. It really sounds like the regulator inside alternator or bad wire to battery.