I suspect the alternator in my '13 GS350 is about to pack up. It's had a slow crank the past week, and this afternoon the battery didn't have enough to start the engine. Got a boost from a coworker, and checked the idle voltage. It's sits about 13.3 -13.5 volts. According to the online chilton repair manual, standard output is 13.2 - 14.8 volts. So, it's just above the minimal output. My car is high mileage for it's age, so I'm not too surprised the alternator is weak now.

From experience, I always thought 13.8 - 14.5 volts was standard. I've got a '96 Camry with over 240k on the clock, and it still outputs 14.2 volts at idle.

So, the question is, what does everyone else get for idle voltage?

 

did u change the battery first? our car is known for failed battery.

 

Yes Sir, checked the voltage after installing a new battery and after a 20 mile drive. Still only getting 13.3v. Even at 65 mph+ it will peak at 13.5v.

 

look like u within specTester Connection
Condition
Specified Condition
Terminal B - Body ground
10 A or less
13.2 to 14.8 V

 

Dude I can only picture someone had 2-5000 watt amps with a cap that killed your alternator other than that I can't imagine why is dyeing already.

 

Yes, 13.3v is still within the standard range, but it’s right at the bottom of that range. I’d like to see at least 13.8v. I’d be absolutely thrilled if it could kick out 14.2v like my old ‘96 Camry.

So, does anyone have any voltage output readings for their cars?

 

Mine (2015 GS350 F sport) was 13.48 with AC (fan on first setting) and high beams turned on, radio on but not very loud.

All tests were on battery terminals.

Then I shut all that crap off and took another reading, it went to 13.51

Motor was at idle too. (car was already warmed up from when I got home from work).

Did you test it under load or just at idle with nothing?

-Mike

 

Just idling at operating temp with nothing else running.

 

Turn the lights and a bunch of other crap on, see what it drops to... if it plummets, then your suspicion is probably correct. A lot of times a failing alt will seem "OK" but then it sags easier under load....

 

I suppose my worries were unwarranted. This morning at cold start, the voltage was right at 14.00v. With the lights, stereo, and seat warmer on, it was steady at 14v. Then as I drove and the engine warmed up, it dropped to around 13.8v. At operating temp after a 10 mile drive it was steady at 13.3v again.

I’ll just keep monitoring the output for a while to make sure everything is ok.

That slow low crank and no start situation has me a bit rattled. But, with a new battery all seems well.

 

I get 13.3-13.8 all the time.

Given our cold climates, I also have a habit of regularly checking the battery and using a Ctek charger to top it up from time to time. No problems.

Do yourself a favor, if your battery is really on it's way out, replace it. Leaving it there will just overwork the alternator.

 

As stated, I’ve already replaced the battery, and all seems well. I’m just not used to seeing anything less than 14v idling at operating temp.

This is is the newest car I’ve ever owned or worked on, and it’s the only one that I’ve seen idle at 13.3v at operating temp.

 

I think you will find that the alternator's output voltage varies with underhood or ambient temperature. As underhood or ambient temperatures increase the output voltage is reduced to 13.8 volts or less. During cold weather charging voltage can increase into the 15 volt range. Thus, depending on conditions a sound alternator will have an output charging voltage range anywhere from 13 volts to over 15 volts.

It sound like yours is working just fine...

 

Some times battery has failed cell showing similar problems.
How old is the battery?

 

it was probably still the factory original battery. So, my car being a 2013 model, the battery/Car we’re built in 2012. That means the battery was at least 5 years old when it quit. That’s plenty of life out of a standard battery.

Now I’ve got a AGM battery. It should last at least 10 years. I had one in my 96 Camry that went 12 years before it quit. I put another AGM in it, and that one is still going after 6 years.