Alternator not Charging (1 Viewer)

[Bill2010Tundra]

ISSUE: Alternator not Charging

I have an issue with my 2010 Toyota Tundra 5.7L that cropped up about 6 years ago, fixed itself and now showed up again. I will state all the facts I can recall and have figured out so far to draw the best picture I can.

Back at that time when it was fixed 6 years ago, the technician had said the problem went away when he wiggled some wires in the steering column. So no real clue to the real issue.


Symptoms:
Battery not charging. Alternator not putting out any higher voltage or is being held down somehow to not allow charging. I can start the engine, but the battery shows on the gauge as about 12v and only goes down slowly with engine running. I can drive but the battery does not get charged. I have to recharge at home.

Still have a number of dash warning lights on.

Windows stuck in position and don't operate. No fan, AC, heat, seat heat, seat does not reposition, no turn signals. Door locks work. Head lights and brake lights are working. I am trying to minimize usage to keep battery up longer.

Engine starts just fine, runs good, revs up good, great running engine. Will not put charge voltage when revved up.

What could hold back charging of battery from there? What else would hold battery at less than 12.6 volts or what would turn off charging if battery it gets lower or is still lower than 12 volts? Is there something else than internal to the alternator that tells alternator to not generate higher voltage to cause charging?

I believed it to be the Battery and Alternator so I had Toyota service check change them out, they tested and agreed they were bad. Now I have new parts there. Still having the same issue. The Technician and another Master Tech took some looks and could not figure the issue. They did not want to spend any further time and my $$ to chase the issue and I agreed with them (at that price). They did not think that the Toyota maintenance phone support engineer service would be able to diagnose or support anything on the issue either.

Thanks for any help or good questions you can offer.
Bill

 

[ToyotaMatt]

check you fuses all of them

sounds like my 05 symptoms all it was a blown simple fuse inside cabin access panel

 

[Bill2010Tundra]

I am not finding any issue with any fuses. Additionally...

I have been testing the Cables, connectors and fuses on this 2010 Tundra and not found anything wrong with them. Question coming up now is about the voltage regulator. Is the voltage regulator internal to the alternator or is it a separate external device? I am finding that the battery does not go down very much while driving the truck, but it really does not get charger either when driving. The voltage output from the Alternator stays about the same as the battery voltage when idle and revving the engine. That is the point where I am now in checking this out, as the same issue continues. Anybody know?

 

[Bill2010Tundra]

I am working to quantify some ideas still. But some more data points and questions at this point:

The battery light is not on, I am keeping the battery above 12v after I drive it any. I have not driven it much. I have only taken a few short drives for checking and to wash off the engine grease for working on. I recharge when I get back home to keep the battery up.

- There are some dash lights on constantly: ABS, Check engine, skid, TPM, Airbags
- Must use shifter bypass to get out of park.
- Odometer is stuck at fixed value - not changed in 12 mile drive.

The battery terminals and ground terminals near battery are cleaned. I cleaned them up after installation of new battery, they had some slight corrosion, but mostly greasy and dusty prior. I have checked some chassis grounds at different places and all are good. I have not checked deeply - like at the alternator - hard to get to, that's next.

Where is the Alternator ground point? I believe it is grounded thru the alternator chassis directly to the engine mount, but looks like it might a heavy wire going over to the battery and then the truck body chassis along with the positive side of the alternator. That makes sense to have both the + and - side alternator to battery connection, but I don't see another wire connection at the Alternator.

That alternator is a tough space to get to, I saw a picture that it has a copper threaded bolt for power connection, but not a separate one for ground, so I assume ground is just to the chassis.

There is also a 4 pin connector that looks like it goes to the ECU for power directly to it and couple other signals. Would this maybe be a control from the ECU to the voltage regulator maybe? Thinking here - maybe the ECU has gone bad. Ouch, that would not be a happy day. So is there a way to test the ECU - DIY wise at home?

I checked the voltage at the fuses. When the power is off, it is the same thru the fuse as would be expected/hoped (on both sides). Some fuses have a voltage when engine is off and the voltage is the same thru. I have not turned on any extra accessories to see any change or voltage drop.

Any other ideas and questions to check are welcomed.

Bill

 

[Jgrauman]

Real quick for my brain with all your words up there.

What is resting voltage at the battery terminals. What is running voltage at the battery terminals

 

[Bill2010Tundra]

Real quick for my brain with all your words up there.

What is resting voltage at the battery terminals. What is running voltage at the battery terminals

Battery sits at 12.9 v after charged up overnight. After 15-20 miles then check at battery it gets down to maybe 12.1 v at the end - engine off when measured. With engine running it is the same steady voltage. So I know Alternator is not charging even when revved up. I have a meter in cab to watch voltage slowly discharge while engine running.

But this is new Alternator and new Battery so I first think they are good, but something is telling the regulator to not charge. ??

 

[Jgrauman]

Battery sits at 12.9 v after charged up overnight. After 15-20 miles then check at battery it gets down to maybe 12.1 v at the end - engine off when measured. With engine running it is the same steady voltage. So I know Alternator is not charging even when revved up. I have a meter in cab to watch voltage slowly discharge while engine running.

But this is new Alternator and new Battery so I first think they are good, but something is telling the regulator to not charge. ??

First, you have a bad battery. 12.6 is a good resting voltage. Below that is bad. You should not have a voltage drop to 12.1 after 20 min.

Second, what is your "same steady voltage" while running.

I'm confused at your comment "alternator is not charging even when revved up" The alternator puts out about 14.4 volts at idle. This in turn charges your battery while the engine is running. If you have a bad battery, which you do, the alternator won't charge it. If you did replace and it was an aftermarket alternator, it's probably bad if you aren't getting 14.4

 

[Bill2010Tundra]

First, you have a bad battery. 12.6 is a good resting voltage. Below that is bad. You should not have a voltage drop to 12.1 after 20 min.

Second, what is your "same steady voltage" while running.

I'm confused at your comment "alternator is not charging even when revved up" The alternator puts out about 14.4 volts at idle. This in turn charges your battery while the engine is running. If you have a bad battery, which you do, the alternator won't charge it. If you did replace and it was an aftermarket alternator, it's probably bad if you aren't getting 14.4

It was actually 45 miles (I just checked) after driving the truck about 30 minutes each way into town this am. I am not so surprised at the voltage going down after 3 times starting the engine and some mileage if it is not being charged. After the engine off and cooling for a couple hours, the battery is back up at 12.6v - I just checked it. It usually pulls itself back up fairly quickly to that after some minimal driving.

Same steady voltage:
Sorry, you are correct, actual voltage would be 0.2 volt higher - As measured by meter in the truck. I have a Voltmeter in the cigarette accessory plug that reads 0.2v lower with accessories on. Then when engine off and no accessories on it reads the same as measuring directly on the battery. Therefore, what I said - voltage does not change from when I turned off the engine. Voltage with engine running and engine off is the same.

Agreed, the alternator should put out about 14+v to charge the battery. It does not and never has since I had it replaced. The old alternator was in that same state. Before this issue, the regulator was charging good, last time I checked was maybe 6 months or more and good at ~13.8 to 14v, I did not write it down. I don't think it has ever put out much over 14v at idle, usually closer to 13.8v at max that I have seen.

Almost points me to the ECU, which does have a signal wire going direct to it. I don't know how I can test the ECU. Is there a self test mode capability?