Alternator Saga - Help! (1 Viewer)

[2002TLCyes]

I've had a grinding noise coming from my alternator area for a while, and although it's been charging fine, I decided it might be time to replace it. I just received a remanufactured alt that I bought on ebay and put it in. Well, the grinding noise went away, but it ain't charging!

Now before I undo and re-do the entire procedure again, is there anything I can check wiring and fuse-wise to rule things out? I know the 3 prong connector was tough to get off and I'd like to test it and see if I'm getting what I should be getting voltage/signal wise on those 3 connectors.

Any other electrical tests I could run would be welcome.. i.e. how do I test functionality of alternator, to single out bad wiring between alt and battery.. Is it a fuse or relay issue? Exciter wire? I just can't believe a reman alternator can be broken to begin with. I must have botched something..

Thanks in advance

 

[kruisinkid]

what brand alternator?
guessing you have a 2002 LC?
the connector on the back of alt can get VERY brittle and literally fall apart in your hands when removing. would be wise to buy a new tail off amazon. there are a couple good youtube videos for testing an alternator. hopefully you have a meter.
while your truck is running, and preferably cold, you should be seeing low 14v range on your meter if its charging.

 

[2002TLCyes]

I have more data. I checked my battery just now and it was about 12.5v. So I started the car up again and immediately started seeing 14.4v on the battery. However, after the car warmed up and slowed its idle rpms, I noticed the voltage started to decrease down to 12.00. I did have high beams on to try to expedite the diagnosis. As soon as I revved the throttle, voltage shot up to 14.4 but as soon as I let go, it dropped rapidly. I turned off the high beams and it seems to have lingered around 12.6. Just finished driving it for 4 miles and have it sitting idling currently reading 13.5 volts pretty steady.

 

[2002TLCyes]

No brand on the alternator. Ebay listing said oem but it’s not..

 

[kruisinkid]

that sounds about right. voltage will drop while running from ~14.4 once battery is topped off and settle to mid to high 13s. 12.6 is absolute minimum for a healthy battery. go for a half hour or so drive around town or maybe 15 minutes on the highway to give it a proper charge.

 

[mbrazil916]

Just in case your plug falls apart, this is the Autozone part number for new pigtail. Just splice and go.

 

[2002TLCyes]

that sounds about right. voltage will drop while running from ~14.4 once battery is topped off and settle to mid to high 13s. 12.6 is absolute minimum for a healthy battery. go for a half hour or so drive around town or maybe 15 minutes on the highway to give it a proper charge.

Ok

I guess it does sound normal, I just don’t ever remember the voltage on the dashboard going as low as it is now with this new alternator at idle.

 

[flintknapper]

Ok

I guess it does sound normal, I just don’t ever remember the voltage on the dashboard going as low as it is now with this new alternator at idle.

Sounds like its working normally (voltage varies). It may not be charging a lot at idle (some remans don't). But you could run your headlights for awhile (engine off to load and partially drain the battery) then start the vehicle and test the alternator output at idle (should be in the 14's). Then you'd know if the alternator is working correctly (at idle) or not. IF your battery is fully charged (or nearly so)...it is normal for the alternator to produce less voltage....but it should ALWAYS be at full battery voltage or above (12.5-12.7)

 

[2002TLCyes]

That’s the thing. I just tested it again and it definitely isn’t charging at idle rpms. The slightest throttle brings alternator output right up to 14+ volts.
I tried to deliberately load the s*** out of it by running high beams, rolling windows up and down, radio in, and fan. The voltage dropped below 12. I didn’t want to kill the battery so I throttled up to charge it again and shut it off.
Why would it not charge at all at idle? Seems like the voltage regulator is bad in it?

 

[kruisinkid]

alternators dont really charge at idle. typically only when you get above 1200 or so RPMs. thats why you always hear stories of people who only have a 2 mile drive to work in a 25mph zone and their battery wil be dead in about a month. look over the charging section of the FSM for test procedures.

thats why i said go take a long drive to top off of the battery. gotta get those RPMs up.
and a no name alt is certainly not gonna be good in the long run.
get one of those cigarette lighter socket voltage readouts and monitor it for a week.

 

[2002TLCyes]

Not sure I buy that. I’ve let my car idle plenty of times for upwards of 15 minutes with lights on and it never killed the battery or even dimmed the lights. Maybe you’re right in that a no name alt would not be good at charging at idle but I think by design the cars are in no way supposed to kill their own batteries if simply left to idle for an extended period of time. Shame that I’m not stuck with this alt. Ebay seller is welcoming an exchange or refund but it’s such a hassle swapping it out that I’ll probably just have to live with it and expect to replace it within a year or two when it inevitably fails.

I did drive a few miles and everything works fine so I guess I just can’t let it idle too long.

By the way the old one looks like a non original remanufactured unit as well. It charged fine with no problems but made a grinding noise. There looks to be pieces of metal shavings floating around in it so something definitely went south inside it but it still functioned.

 

[suprarx7nut]

That’s the thing. I just tested it again and it definitely isn’t charging at idle rpms. The slightest throttle brings alternator output right up to 14+ volts.
I tried to deliberately load the s*** out of it by running high beams, rolling windows up and down, radio in, and fan. The voltage dropped below 12. I didn’t want to kill the battery so I throttled up to charge it again and shut it off.
Why would it not charge at all at idle? Seems like the voltage regulator is bad in it?

This is normal behavior in my experience with the LC and a host of other 90's Toyota's. The alternator may not provide a lot of charge at hot idle. Totally normal with a good alternator. It should maintain voltage indefinitely, but not necessarily add much charge to the battery.

Alternators in general are not necessarily designed to "charge" batteries so much as maintain them. You will improve battery longevity if you use a plug in battery charger in your garage. IMO, a nice battery charger is a good investment for anyone with access to an electrical outlet near their parked car. Charge up your battery every few months and you'll get more life out of them.

The FSM alternator test authored by Toyota allows down to 13.2V from the alt terminal to ground while at 2000 RPM. There's a good reason they don't list a test at a 600 RPM idle. See attached.

 

[94FOURBY]

I hate to even weight in on this but a Toyota alternator should charge from 13.2 to 14.8v at idle. The pdf from the fsm(above) states this clearly. If it doesn't or if it only has 12v there is a problem. I'm not saying the only problem is the alternator but there is a problem. I would use the pdf above and check everything.