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2001 ES300, 171k miles. Car has always been in the family and well maintained.
I replaced the alternator 3 years ago w/ rebuilt one from O'Reilly. Yesterday replaced again. The 3-year old alternator failed their bench test. Prior to pulling alternator I did a multimeter test and was only getting 12.4 at idle. Only test done at home prior to pulling the alternator out.
Now the new alternator is only giving 12.4-12.6 at terminals and is certainly not charging. After the car sat overnight I was briefly getting 14.5V at terminal, but as soon as I put a load on the system that dropped to the 12'sV. Even w/ no load I was unable to reproduce anything above 12'sV after that initial reading.
I took car back to O'Reilly and they tested the battery/alternator system. Test came back as a bad voltage regulator. Tech said almost always that means a bad alternator, but to confirm I need to take back out and do a bench test. Explaining my issues, he's thinking we may have another issue. I'm not confident on his expertise. Certainly not confident in mine.
Using multimeter, I get the following readings:
- At 2000 RPM's, w/ no load terminal to terminal will hit 13.5V. Under load (AC, Lights, Stereo) it is mid 12;sV.
- Positive at alternator to negative battery terminal at idle is about same as above.
- Positive at alternator to engine and other grounded parts is about same as above.
- Drop test red-positive terminal to black-positive alternator reads .4V. What I've read is this is a problem. Shouldn't go above .2V. How do I fix this?? Cables go to wiring harness. Looks like huge job.
- Drop test black-negative terminal to red-alternator body reads .02V. Does this mean the ground is good?
Other observation. The wiring harness that plugs into alternator has some white paste type material on it. At first I thought this might be the problem (corrosion), but it is definitely a wet paste. Is this possibly some type of conductive paste there on purpose? Dialectic grease is usually clear, right? Can I buy the harness and just splice the wires? Not sure how to clean it completely.
If the problem is with the drop test bad reading (positive to positive) then why don't I get a good reading when I go alternator to engine? Completely bypassing the wiring b/w the alternator and battery terminal.
In the last 4 years this car has gone through 4 batteries and 2 alternators. Plus we get a lot of trac light, abs light issues along with the occasional check engine light codes. Usually you can reset and they just go away. Is there something in the grounding now that's causing all these issues.
Tonight I'm going to pull the alternator and take to O'Reilly in the am. If I'm lucky, they gave me a bad replacement. However, I'm very skeptical at this time. Thoughts and guidance is greatly appreciated!! This is my son's car and he wants to take to college next year (1500 miles away). Car is really good cosmetically w/ new transmission, brakes, water pump and tires. But at some point I need to stop the bleeding on a 17 year old car.
Buy a Denso reman or do an alternator upgrade* which is well worth it your engine will run better. Lexus outfitted this generation ES with an insufficiently powerful alternator. The goo you see in that connector is dielectric grease. Voltage drop testing is unreliable if you have a cheapo test meter, which most of us do. Anything below 1 volt will be subject to a large margin of error. I can test the voltage drop in my ES if you're curious.
* I have this 130 amp unit on my Lexus highly recommended. Technically I should upgrade the wire from the battery to alternator but have not had any issues. Worst case it blows the fuse.
Out of curiosity I went out and did some tests. I get a 0.387 volt drop at idle no accessories turned on. With everyone on (lights, high beams, seat heaters, hazards, rear defrost, max fan etc. it went to 0.82 volts. That seems too high but I don't have a reference. On the plus side the alternator maintained 14.24 volts which is great. But that drop scares me. Not sure where the main line is routed it gets lost in the loom when I try to trace where it goes.
Another way to see if it's a bad VR is by simply looking for leak-through AC voltage at the battery. No need for a bench test if that is present (and that is what causes the weird electrical anomalies).
Sequential bad alternators with defective voltage regulators are normal from O'Reillys. Their units are very poor quality. I am on my 2nd and wondering when the 3rd will come up - I will probably just rebuild it myself to avoid future hassle and eat the cost). As mentioned, a bad VR can explain the other prior symptoms (TRAC light, etc.).
Another way to see if it's a bad VR is by simply looking for leak-through AC voltage at the battery. No need for a bench test if that is present (and that is what causes the weird electrical anomalies).
Im assuming the VR is in the alternator on these models, correct??
How do I check for leak-through AC voltage?
Also, by checking voltage directly from alternator and grounded to engine tell me the alternator isn’t putting out enough voltage, or is it possible the alternator has an issue related to the wiring harness?
Get a proper alternator your problems will go away. The Denso reman from the RX is a direct fit, get the 100 amp or the 130 either way much better than stock. If that 100 amp fuse is blown your alternator won't charge at all.
Oreilly returned the alternator and sold me the 100amp RX version. This only cost me $40. I didn’t want anything higher since the Alternator main fuse is rated at 100 amps and would have also required me to order online.
I’m getting much better readings, but there is definitely a voltage drop b/w the positive alternator terminal and the positive battery terminal. The voltage drop test no load, idle is .4 and jumps to .8 under load and 2k rpms. Under load and at 2k rpms I’m getting 13.6V at the battery & I’m getting 14.3V alternator positive to ground.
Ground drop test is .06.
Somewhere in a Camry forum someone posted they had a cracked main alternator fuse. It looked good with a visual inspection. Is this fuse b/w the alternator & battery? It’ll take some work since that’s bolted in, but shouldn’t be too hard. I just see that as an unlikely culprit.
What else should I check. The wiring harness looks like a heck of a job to try and chase.
I got a an electrical expert to come take a look. Drop was now only reading .2 with both his meter & mine. Mine showed slightly more, but his was clearly better.
All his readings show everything working and said upgrading to 100amp was a good idea. He said the reason for my low drop rests may have been battery related. Probably not fully charged.
Hopefully this helps someone in the future. Now on to fixing a couple of other issues he pointed out. Nothing majors and all DIY.
I had a few issues due to a bad battery from advanced auto (they installed).
After fumbling around for 2 weeks i changed the alternator. I eventually found out it was the battery. It was leaking which caused a ground short. Blew a couple fuses including the 120amp alt fuse.
I finally got it up and running but i have no radio and some of my lights are out for the temperature control.
The stereo is after market i have good stereo fuses 1 and 2 in the fuse box and on the back of the receiver, I have the voltage going to the receiver, and I have hooked the factory receiver back up and still get nothing. Someone point me in the right direction please!
Aftermarket stereo is pretty easy to bench-test - connect ALT, B+ and Ground wires to the battery, if it will start up, then the radio is working and one of those 3 wires went bad on the car. If, however, it won't, it may indicate that the radio got toast together with other fuses.
As for the climate control, all those lights are powered from the same source, so if only one or two of them are out, it means that the issue is in the Climate Control Unit itself. Try taking it apart, I am not sure of those lights are still serviceable like they were in the previous generation, but in either case it should be possible to measure their continuity.
The climate control lights are serviceable and take a little bit to get too but it’s not too bad of a job.
The problem is finding bulbs that fit. I ordered some from the dealer and they are close but not exactly the same. They don’t latch in place during the last little bit when turning with a screw driver and fall out over time. Ended up going to a wreaking yard and pulling some.
I have a 2000 Lexus ES300 and have experienced the same issues. I have replaced the alternator with Oreillys 5 times. This last time the alternator only lasted 45 days-ish. I always bring it back and after pulling my battery and charging it over night they explain its a bad alternator. So after reading this thread and other like it I hear the same suggestion to use the RX300 100 amp alternator so that is what I just did. After it cools off outside I will be out there swapping it out for the 100 amp alt. My question to others that have used this fix is the belt and pulley issue. Being that it has a smaller pulley has anyone had issues with using their belt on it or does the tension bolt provide enough distance that it doesn't matter? Seems like it would as its marginal but I am anxious to find out if this solves the issue or not overall. I will provide and update later. Thanks again for all the suggestions.Ii have tried everything to correct this issue so I hope this is it. I am about done with the car.
06-30-18, 11:13 AM
ES300 Charging/Alternator issue???
