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intermittent charging of the new alternator


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lukasznas
New User

Jan 10, 2023, 3:47 PM

Post #1 of 8 (1195 views)
intermittent charging of the new alternator Sign In

Good day,

Toyota Rav4 2008 2,4 engine.

Replaced alternator (myself) after confirmed the old one stopped working completely.

1st day of new alternator all good, confirmed voltage 14.4 VDC.
2nd day morning I measured 11.8 VDC. Started the car again and it went up to 14.3 VDC.
Next few days noticed alternator was sometimes charging, sometimes not. I have to add that I also heard noise when alternator kicked in.

Decided to give the car to mechanic, who checked the charging system, run testes and told me everything was fine. When I told him about my findings, he said that computer decides when the alternator should start charging. Is this really true? I always thought that alternator starts charging as soon as I start the car.

With that info from mechanic I just used the car for about 3 weeks. I should also add that I use the car mostly to drive to and from train station which is 1,5 mile away. Short trips every day. I also noticed that noise was now less quiet.
I never confirmed that but I am pretty sure that noise is when the alternator kicks in.

Last weekend the battery sign showed up. Measured battery below 12 VDC, bought the battery charger and restored it to full capacity.

Now I observe again, in the morning mostly I notice the alternator doesn't charge right away. Sooner or later the battery will die again.

I'm really confused with what is happening.
Any advice would be appreciated.
Thank you.
Lukasz


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jan 10, 2023, 4:38 PM

Post #2 of 8 (1182 views)
Re: intermittent charging of the new alternator Sign In

Your mechanic was correct about how this charging system operates. The PCM turns it on and off as required but the battery light is not supposed to come on.

If that keeps happening you may have gotten a defective alternator.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



lukasznas
New User

Jan 10, 2023, 5:12 PM

Post #3 of 8 (1161 views)
Re: intermittent charging of the new alternator Sign In

Thanks for responding.
I'm just wondering if the random turns on and off are the symptoms of bad alternator. My understanding is the PCM tells alternator to start charging when battery level drops below certain voltage ?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jan 10, 2023, 5:18 PM

Post #4 of 8 (1159 views)
Re: intermittent charging of the new alternator Sign In

No, the technology has changed recently.

Old systems would vary with load,RPM and battery condition. These new ones are programmed to know when to turn on.

If you are testing it and see that it isn't charging, change the load and see what happens.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



lukasznas
New User

Jan 11, 2023, 3:48 PM

Post #5 of 8 (1095 views)
Re: intermittent charging of the new alternator Sign In


In Reply To
No, the technology has changed recently.

Old systems would vary with load,RPM and battery condition. These new ones are programmed to know when to turn on.

If you are testing it and see that it isn't charging, change the load and see what happens.


I did applied full load (AC max speed, lights and radio ON), still not charging. Although It started charging only after I shut down the engine and started it again. It looks like its totally random.
What do you think ? Unimpressed


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jan 11, 2023, 3:52 PM

Post #6 of 8 (1091 views)
Re: intermittent charging of the new alternator Sign In

If you're suspicious of it, take the alternator back as a defect and get a new one . See if that's any different. I'm sure it has a warranty.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



lukasznas
New User

Jan 11, 2023, 3:55 PM

Post #7 of 8 (1087 views)
Re: intermittent charging of the new alternator Sign In


In Reply To
If you're suspicious of it, take the alternator back as a defect and get a new one . See if that's any different. I'm sure it has a warranty.


thank you


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jan 11, 2023, 5:17 PM

Post #8 of 8 (1074 views)
Re: intermittent charging of the new alternator Sign In

I don't have a way to test off car Autozone by name, others too, does offer that but nobody knows how to use the machine!

Failure rate of cloned ones is high so test working them can't just ground a wire on this car older ones you could so work it with blower motor, all lighting on + RWD watch it's performance.

New or rebuilt (not common to me now) you fixed the old one but now the parts just brushes and diodes + perhaps a bearing minds explode at the thought of that!

Tom







 
 
 






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