Charging issues not the battery or alternator? (1 Viewer)

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Ive got a weird charging problem, I thought was the alternator, but i took it to autozone- and it tested good. apparently I have a code for an open EGR, so they tried to sell me a new egr LMAO i dont think thats it) the battery checked out good too... So looking for some advice.

Started noticing the AC fan wasnt blowing as well and the engine was sluggish with gas, looked down and the [DC voltage] was only at about 12.3. Then it jumps to about 16 before going to 14.4 and holding for about 5 seconds, then back down to 12volts for a good while. It repeats this cycle regardless of what is plugged in.

Terminals are clean and tight, as are the engine grounds ... so im kinda stumped. seems to be a repetitive cycle regardless of what is turned on or off, and my mind is telling me its the alternator, so before I went to the effort of pulling I thought Id ask if anyone else might have experienced anything like this before?

FYI- im running the tundra 150A with photoman bracket ,alternator is 4 yrs old rebuilt OEM denso, prob 30K mi, and batttery is a 10 mo old duracel from sams club.
 
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Road Apple

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Have you replaced the fusible link in the last couple years. They tend to deteriorate slowly over time.

Are you running stock ground wires? You might trying to add an additional ground wire from the battery to the engine block.

The “Big 3” wires are worth checking and upgrading, especially with your increased loads.


 
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Are you running stock ground wires? You might trying to add an additional ground wire from the battery to the engine block.

Have you replaced the fusible link in the last couple years. They tend to deteriorate slowly over time.

The big 3 wires are worth checking and
upgrading, especially with your increased loads.
howdy- yep the fusable link was replaced with a marine fuse when I did the alternator upgrade a few years ago, and all the engine grounds were replaced with 1AWG cables then as well. they are tin plated copper, and no corrosion on anything. I even tested resistance on any cable i could reach, and they are all in good shape.

Wiggled every cable with the engine running and volt meter attached and no change.
 
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Watched “WonderHussy” on YT and she took her 4Runner there to check her alt. Said it was good, she leaves, and truck dies. Takes it somewhere else and they say alt was no good. Replace alt, truck dies again. Turns out it was the battery IIRC. I would get the alt/battery retested.
 

Road Apple

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A bad voltage regulator acting up in your alternator?

Here’s what @cruiserdan had to say on a very similar problem.


A fully charged battery should indicate 12.67 volts. Your reading is below that. A battery attached to a running engine should indicate well above that mark. Your readings are indicative of either a sick battery or an alternator that is not "putting out" (so to speak :D ) Or perhaps an abnormal electrical load.

The cheapest "test" would be to replace the brush package. Also an assesment of the battery age and charge condition should be made. Since the voltage increases with RPM I suspect that the diode-trio and the voltage regulator portions of the alternator are functioning.

D-“

 
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I wouldn't trust an "alternator is good" / "alternator is bad" test done at an autoparts place.

Put a multimeter (on DC volts) ground probe on the engine block (scratch to make good electrical contact) and the positive probe directly on the Hot output of the alternator with the engine running. It should be around 14V give or take a few tenths depending on temperature and battery state of charge. Report back with the reading and whether it is steady or jumping around. Then do the same across the battery +/- posts.

And your 12.3V is not an "amps" reading, it's a voltage reading. Where are you reading that value? OBD2 scanner or ?

cheers,
george.
 
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Started noticing the AC fan wasnt blowing as well and the engine was sluggish with gas, looked down and the amps are only at about 12.3. Then it jumps to about 16 before going to 14.4 and holding for about 5 seconds, then back down to 12volts for a good while. It repeats this cycle regardless of what is plugged in.

Assuming these measurements came from a steady idle condition, I would say your alternator is bad. Specifically, the voltage regulator. I don't really see worn brushes or a battery causing that sort of cyclical behavior. Also, I don't think you should see voltages spike that high with a solid state regulator. Certainly not repeatedly.
 

Broski

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Assuming these measurements came from a steady idle condition, I would say your alternator is bad. Specifically, the voltage regulator. I don't really see worn brushes or a battery causing that sort of cyclical behavior. Also, I don't think you should see voltages spike that high with a solid state regulator. Certainly not repeatedly.
This ^^^
 
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It probably is the alternator. If it were me, I'd swap in the battery from a different rig and see if it continues to show low voltage. Easy and free diagnostic, but then again, I have lots of rigs to steal from. If still low, replace or repair your alternator.
 
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I wouldn't trust an "alternator is good" / "alternator is bad" test done at an autoparts place.

Put a multimeter (on DC volts) ground probe on the engine block (scratch to make good electrical contact) and the positive probe directly on the Hot output of the alternator with the engine running. It should be around 14V give or take a few tenths depending on temperature and battery state of charge. Report back with the reading and whether it is steady or jumping around. Then do the same across the battery +/- posts.

And your 12.3V is not an "amps" reading, it's a voltage reading. Where are you reading that value? OBD2 scanner or ?
Cheers, George, thanks- that is one I havent tried yet but since its grounded to the chassis I hope it would say the same as at the battery terminal... I guess ill see when I try. I agree I think its going to turn out to be the alternator. I dont really trust the AZ test either, they were just there when I noticed it and asked them to pull codes. I find that bigger alternator a bit of a tedious PITA to remove so I was in denial of having to do it again. looks like mt PS pump has a nice ooze to it too, lucky me... yes i must have mispoke and meant DC volts, all my readings are with a digital multimeter under the hood at the battery.
 

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