sbagdon

Having what we believe is an alternator issue, yet confused...

Car has been running great, until last weekend.
Short errands, last errand, starter sounds slow/weak, look down... battery light.
Alternator does not appear to be generating 14v, if anything
Battery light does not appear to turn on until <12v....?!
Measure battery running/off, <10v.
Car will run until about 9v-10v, then slowly idles down.
At 400rpm-500rpm, power off, and attach to battery charger
Battery will charge fine up to 12.5v (charger does 12.5v, not 14v).
Repeat... starts/runs great, yet no charging, slowly discharges battery.

Does this make sense, that if the alternator were bad, that the battery light would not turn on, until 12v?

Past experience from all Toyota/Lexus vehicles has been the battery light will turn on, under any condition the alternator has failed, and is not producing 14v+.

Thoughts?

Thanks!

firelizard

iTrader: (1)

Have you had the battery checked?

sbagdon

Not yet, thought of it, doesn't make sense. If the battery were going, the alternator should go to 14v, charge the battery to 12v, and then the battery wouldn't have the CCA's to turn over the engine. Battery stampings shows it was replaced just before we bought the car, backing up the sellers claim.

Can get a (new) re-man alternator on eBay for $89 (free shipping), and the car has 210k+ miles, so it's probably the original. Will probably end up pulling the alternator and battery, having them both tested, then replacing the alternator proactively, and the battery only if it doesn't test well.

Yet still wondering why the battery light doesn't come on, if the alternator isn't charging.

firelizard

iTrader: (1)

I would test the battery before removing the alternator if only because a) having a battery tested is usually free, and b) removing just the battery is a lot easier. Then you can rule it out and move on to more labour intensive testing.

Mike246

If I can stick my 2 cents in, the most basic tests are the most revealing.

Your battery should measure 12-13 volts with the ignition off. If it's lower, either it's dud, not being charged or you have leaking current (see below). With the engine running on a fast idle the voltage at the terminals should be 13.5 - 14.5 otherwise you have a broken alternator.

Have you inspected the fanbelt?

Leaking current - possibly a trunk light, interior light or similar being lit when the car is not being used. It's not unheard of.

Konrad1

Do not write off whole alternator yet, it's usually regulator dying. Lexus is sharing regulator with many other Toyota's as MR2, Supra, Corolla etc. Any chance you can show how your 3 pin plug at alternator looks like? I changed regulator on my Supra for a total cost of 17 pounds....

sbagdon

Battery is coming in at 12.6v with the motor off, with no increase of voltage while running. Between testing cycles, it goes on a maintenance charger, to get it back up again. With 200k+ miles, it's probably time anyways. I'll know when the alternator is pulled, if it's Toyota, or an aftermarket.

Agreed. Yes. No.

Bought a re-man unit from eBay for $89 (shipped, no-core), so I'll keep the old one if it's Toyota, and rebuild it locally. Yet we'll keep this car for a while, and are thinking at looking at other 400s (maybe an SC), so it's not like the alternator will go to waste.

shwalker07

I highly suggest you buy a battery/alternator tester. They are super small to store and very cheap now to buy. Topdon makes a great digital one. You can see the overall health of your battery when you put in the cranking amp rating and see what it is actually putting out. I check it twice a year so I know when to expect to get another battery (especially since one of my AutoZone Gold batteries is from 2013 lol).

If you plan on keeping the Lexus for awhile, a remain Denso alternator from RockAuto is where I bought mine for the best price. Those remanufactured ebay alternators have who knows what inside them from who knows where and usually don't last that long.

sbagdon

I'll look in to it, thx!

sbagdon

Did the alternator last night... 3hrs of fun. Made the joke.. .this job would have been 20min, on the '00 Camry 4cyl...

Not difficult, just... cramped. Releasing the power steering hoses from the oil pan made it possible, yet still a bear to get it out, fighting around the radiator shroud. The power steering pulley caused the most stress, yet was able to get it off without a puller, just some persuasion, as the pulley was rotated, to apply equal force across the entire splined shaft, just finally slipped off. One note... will have to fix the power steering leak, it was a mess all around there, and that might have contributed to the final demise of the alternator... yet that might wait 4-6 weeks, when we do the timing belt.

Some times, it's the simple things... after putting all the important stuff back, started up great, and was putting out 14v+, then wrapped everything up. The old alternator was a genuine Toyota/Lexus part, so either the original alternator lasted 200k+, or the last person to change it paid-up for a genuine. Yes, we kept the alternator, and will get it cleaned up and rebuilt, and might put it back in, yet at least the car is drive-able... it's hot here, and the primary backup car doesn't have a/c. Yuck.

Yet we're stuck with this conundrum... the battery light does not light when the alternator is low, it lights up when the battery is low.

Before the swap, the battery terminals were showing 12.2v (and dropping) and no battery light. After, it was showing 14v+. That just seems wrong.

Thoughts, anyone?

Thanks!

shwalker07

A good normal charging system will put out 13.5v to 14.5v. On my Lexus I did the volt meter display mod and during the night with the headlights on, I will normally see 13.5v. With the headlights off driving around during the day, it is around 14.1v then.

sbagdon

The issue was, the battery icon on in the cluster wasn't lighting until about 11v. Much rather know that it's bad at 12.5v, when either moving, or after starting. Yet thanks for pointing out the volt meter mod, was thinking, at this car's age, of doing something like that.