I have this Battery Discharge light come up, next to where Check Engine and other indicators are located. I am planning to take it to my Mechanic and will get the codes from AutoZone tomorrow as well. It is 2002 RX300.

Anyone have any idea what might be the potential problems are? and if it would be ok to drive the car? I heard about Alternator may be the culprit?

any idea about the cost to replace or fix this problem.

 

Since the check-engine-light (CEL) isn't on, I doubt you will have any CEL codes coming up.

Are you using the original battery? If so, after 7-8 years I think it is time to replace it. It could be the alternator, but it could be the belt that drives the alternator, or other things. Have you replaced the two accessory belts? Have you looked for signs of belt slippage?

A replacement battery at Costco is about $65. Having an independent mechanic do the two accessory belts might be $120. I'd recommend using the same belts Lexus dealers do, but that's just my opinion.

Does the alternator light dim when you increase the rpm?

 

Do not confuse the CEL with other warning lamps. CEL is lit typically based on emission [fuel, air, timing] issues.

The battery discharge indication is exactly what you guessed .. alternator not providing enough charge to the battery.

I drove about 20 miles with only battery power [day time ... so the battery was running everything day-light-running, fuel pump, etc.]. Close to home all warning lamps lit up and as I pulled in the driveway every thing went dark.

So check the belt and battery connections. If they are good, then most likely it is a bad alternator.

Salim

 

Thanks a lot, Bob and Salim Shah for this helpful information. I took it to my mechanic and he mentioned it might be the alternator. So I asked him to replaced it, The total cost came out to be $350. Since then I drove few more miles and the same warning light came up again this morning. I am planning to take it to him again this evening.
Any clues? also I trust this mechanic as he has been doing my cars for the last few years and I never have any problem with him.

 

Did he bench test the old alternator to confirm it was bad? Or just replaced it because you told him to ?
If the alternator was proven to be defective, then there is a good chance the battery was damaged and will not take a charge from the new alternator. Did you , or your trusted mechanic check battery voltage?

 

If you just asked him to replace the alt., I would suggest that you let him do the diagnosis. Hope that's not a $350. lesson. I don't think the warning light would come on if the battery were damaged by an alt. not charging properly. 1st. thing, it wouldn't have started after the alt. replacement, and 2nd, if the alt. is charging properly, even if the batt. is bad, the juice just flows through the batt. when it's running, it's actually being feed by the alt., not the battery, which is primarily for modulating the flow of juice and starting the vehicle. The alt. should have a fuse, probably under the hood, that is a rather large capacity fuse, but probably not the problem because if it were blown, the mechanic would have seen that the light was still on after he replaced the alternator. This takes diagnosis that is a little hard to do from hundreds or thousands of miles away.

P.S. If he used a rebuilt alt., there are plenty of BRAND NEW rebuilt alternators, out of the box that are junk. Too much cheap labor rebuilding them and too many cheap foreign parts that they are rebuilt with.

 

If you have used the mechanic for years, then he must have earned your trust. Take it back and have him look at it again.

I too have little faith in the rebuilt stuff. They do come with warranty, and you should not be charged for labor twice. So in some way it is costing your mechanic too.

Salim

 

It was the case of loose battery connections, second time around. Now I am bit worried that the mechanic hasn't done the proper diagnosis first time around but anyway I see that he replaced the new alternator in the car. I guess I learnt my lesson.

Now I am hearing another sound coming from under the hood, especially when I speed up the gas. No sound when in reverse gear. I talked briefly about this to my mechanic and he checked few things under the hood and he mentioned that sound is coming from Transmission assembly (I hope I am using the right words) and torque converter needs to be changed, which is itself pretty laborious Job, The part itself cost around $300 but the Labor cost is a killer here.
Now I am thinking of taking my car to Lexus stealership and let them properly diagnose the car.

 

Battery terminals have a simple test ... If you can twist the terminal by hand then it is loose.

Salim

 

well my battery light came on, so i had my battery tested at 3 different places to make sure(tested good every where) and then i had all 3 test my alternator( tested good also). I checked the alternator fuse, and ground and terminals but nothing. I replaced the belt thinking maybe slippage was problem but nothing. Got any ideas?