Hi everyone,

Could someone here use a voltmeter and let me know the idle voltage on their ES 300 model year between 97 and 01 WITH all accessories on (blower fan on high, defrost, at least 1 heated seat) while the engine is hot and idle is at the 650rpm mark?

I am trying to determine if my charging system is problematic or if it is normal to have low voltage on idle with multiple loads on this car with the regular spec 80 amp alternator.

thank you for your help everyone.

 

Before I put in a 130 amp alternator at similar loads to what you describe I got about 13 volts maybe a bit less.

 

thank you very much for your input. Can you tell me if your charging system was fine when you did that measurement, and if you just upgraded for the additional power?

I get around 12.9 but it drops rather quickly, the 80 amp definitely isn’t able to supply enough power at idle speeds and I suspect my battery is not doing great in the Canadian winter (though it goes back up to 14v when sped up).


Thanks again.

 

100 amp upgrade is enough 130 is overkill but the price was right so I got that one. Now I can't make the alternator go below 14 volts at all, although I am a bit leery of cranking absolutely everything electrical to max since the original wiring is not designed for 130 amps. Under normal use I have not had any issues, also the engine runs better since the 80 amp is barely adequate for the car. FYI the alternator upgrade comes from a 1st generation Highlander (and I think the Sienna) either way easy to find just get one that has the same plug as yours.

Going from memory I got the Denso 2100-466 I don't remember the 100 amp part number check rockauto

 

Hello,

I just ran some tests on my stock rebuilt alternator, it has new OEM brushes, rectifier, and voltage regulator. I switched on all the lights that I could, radio and climate at maximum, and my voltage dropped to ~11.9V, while also dropping the idle speed. I switched off climate control and got ~12.5V... Basically that is why I got a new alternator in the first place, but it didn't seem to help much.. Granted, I knew that it is not that hard to upgrade it to 100/130A, but never in my life I thought I would need it.. Maybe I should trade my rebuilt alternator for the one off of Highlander/RX..?

 

Required upgrade IMO.

 

2000 RX300 here.
Ive had my fair share of alternator woes.
2 reman replacements (warranteed) in 3 yrs before upgrading to a brand new unit.
Duralast GOLD. 100amp rated. (4 months ago)
I installed a volt meter after that to monitor it.
Readings are within .05-08 between my FLUKE meter.
Headlights, blower high, driv seat heater, rear/side mirror defrost, radio all ON.




With the wipers on, voltage drops to 13.1
With the said acc. all ON, voltage is at 14.3 at 1500 rpms.
No load (DRL’s on) just sitting at idle. 14.4-14.5
24F battery

 

My two main groans about my ‘05 are no voltmeter and a rather silly cup holder.

 

Wow, thank you everyone for the responses. It does seem that this car requires a top-shape battery to barely keep loads on with the 80 amp alternator.

it’s not unusual to turn on heated seats, the blower motor and rear defrost in winter time, but it seems like Lexus never thought that would happen!

thanks everyone.

 

Some updates : I bought a brand new TYC brand alternator for a highlander/RX and fit it, but unfortunately I’m still getting low voltage at idle with heavy loads. Headlights, Heated seats both high + rear defrost + AC ON and I get between 12.3-12.6 volts. If I turn on headlights and AC only, it does sit around 13.6-14.2.

tested all my circuitry and it seems like everything is good on that end so I’m not sure where to go from here. My voltage drop does get around 0.3v with heavy loads, which is a bit higher than I’d like, but it’s hard to believe that would cause this much of an issue.

anyone experience something similar and find anything out of the ordinary?

 

Anything other than a Denso is suspect right out of the box I've seen them be DOA brand new including TYC.

 

Not entirely sure how or what you are measuring. Full electical load with unnecessary accessories at idle is not designed for extended periods.

But to bottom line the thing, check the output AT THE ALTERNATOR (not across battery terminals) at idle. If less than 14.x (I would say 14.2, you can argue), then return the alternator.

Check at the actual alternator before you decide low voltage in the system is becuase of the alternator and not something else.