Charging Issue with New Battery and Alternator
 

I'm really stumped. My 4Runner will not put out enough power to charge the battery or run correctly. Background:

1. Swapped in 2 different alternators. All three put out max of 12.5V while driving (observed via OBD-II reader), used to be 13.0V. At idle it will drop as low at 11.8V, used to be around 12.7-12.9V. So it's not charging

2. Replaced dead battery with a new Optima Yellow top. No difference. Swapped in another known battery that's good, no difference.

3. Checked all wiring and there's no issues. Did the big 3 wiring 3 years ago so I've got some redundant wiring so at least one would work fine if the other failed, except for maybe the ground?

4. Alt fuse (100 amp) is good.

5. If I drive it more than 20 minutes the battery starts to drain and I have to put it on a charger overnight (don't want to kill my new battery).

It makes a whirring/whining noise that started when the voltage started dropping. Started out sounding like an intake whistle. Now it's a straight-up whine at low RPM's and is coming from the alternator side of the engine. I have no clue what to try next other than start randomly replacing fuses. The Alt fuse (100A) won't come out and I don't want to break it though.

Sounds like they're all bad. Have they been tested?

The fact cannot be escaped that all the alternators thus far tested are putting out deficient voltage. My knowledge isn't vast enough to know if there is another bad part or system that would cause a perfectly good alternator to suddenly put out 12.5V. BTW, 13V is also inadequate while running; should be at least 13.5 on a very hot day, up to 14.2 or 14.3 when it's cold. Maybe get a "new" alternator with an E-Z return deal?

I did. The third alternator I tried today was a warranty replacement. 3 alternators all bad (including the original one) is too much of a co-incidence for me. A month ago the voltage was perfect.

Also, the voltage is being measured from the OBD-II port. It's going to be a bit lower than say the battery voltage.

The connector on the back of the alternator with the 3(??) small wires. Isn't there supposed to be battery voltage fed TO the alternator on one or them to make the alternator work? Maybe broken wire on the connector or problem farther upstream? I don't have a wiring diagram handy.

Shot in the dark here, trying to think of common things between the 3 alts.

Yeah I wondered that too. Any way to check the wires you think? The FSM did not have any suggestions or procedures.

@TheDurk wondering if you had any advice since you tend to know electrical issues pretty good...

Check to make sure your charge warning light successfully completes the bulb test when you turn the truck to on (not start) - that light is part of the exciter system of the alternator. If that circuit is not complete, there's no seed charge to energize the windings of the alternator and you may not get charging.

You really need to have idle no lower than 13.2v. So you may have had a problem that has been present for some time but finally manifested itself to be seen.

Parasitic draw?

I would start with your big three wiring. Remove and inspect your cables.

Given that you live in CA I doubt you have the green electrical crustiest but I would remove the fuse block and look underneath as well.

You should check battery terminal voltage with a volt meter and not go by the reported voltage on your scanner.

I usually have a usb Charger that reads system voltage when it’s not charging my phone.




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Are all the alternators you tried aftermarket?

The battery light on dash should function and if the light is blown, then the charging is getting affected.

The big-3 wiring might causing an issue.

Try checking the output of the alternator at the main output on the side of the alternator with a volt meter.

What is your Amp draw with everything off?? Hook a digital amp meter up with everything dead in series between the terminal and the battery... Should be extremely low millamp draw (20 - 50ma)

If you have extra circuits added. Disconnect them and check to see which is pulling it down.

These rigs really like their Denso alternators but it is possible you have added so much extra current hungry addons that you have far exceeded the charging system of the vehicle. :D

Do you have any idea how much current your a pulling with all your accessories on?

I am guessing you either have some shorts or you are pulling way to much current and frying your alternators.

TheDurk will know when he gets here.

You could backprobe the connector when the engine is running but you are going to need to know what to look for....

Taking a look at the crude EWDs in my Haynes manual you do need some feedback through the small 3(??) pin connector. It looks like the ALT-S 7.5A fuse, the Guage 10A, and the IGN 7.5A come into play. Maybe make sure they are all OK. I have read about broken wires right on the connector, maybe a good visual will turn up something.

Did some more testing this morning. I think it's somehow temperature related. I also replaced the ALT and STARTER fuses in the engine bay. I need some more fuses then I'll replace the GAUGE and IGN fuses next.

At cold start, I got 14.5V across the battery. That tells me the alt is good right? Read as 13.0V on my OBD-II, just like it always used to. I put a load on it by turning on the headlights, rear defroster and my 55W light bar. Doesn't budge a bit. Awesome.

Driving to work I see it slowly drop to 12.2V on my OBD-II. When I get to work after 10 minutes of driving, the battery voltage is down to 13.7V on the battery in park. In gear, it dropped all the way down to 13.1V with headlights on. The whinning noise gets louder the hotter the alt gets. Also, are alternators supposed to be so hot that you can't touch them after 10 min of operation?

I did check that and the dash light comes on like it should. It does not come on while driving though, even when the voltage drops. Maybe because the battery is brand new?

Ha, yeah no crusties here. Not a spot of corrosion or rust anywhere.

The big 3 wiring I have is redundant except for the battery->ground wire. I have two power wires from the alternator as well as an extra ground wire from the alternator mount to the battery terminal. What would be an unacceptable amount of resistance in a large gauge wire?

The odd thing is it's been great for years. I did the big 3 wiring about 3 years ago when I added my stereo system since I put in two small amps. Worked great. When I added the e-fan, the old DENSO unit wasn't putting out enough amps at idle (would bounce back up when I would get on the gas though) so I put in a CS144. Always read 14.2V or higher at the battery and around 12.8V - 13.2V in the vehicle. Has been perfect until about a month ago when I noticed a slight whistle noise that turned into a loud whine at low RPM. The voltage started dropping at that time and killing my battery. Something's gone bad in the past month I just can't find it.

I did disconnect all the accessories but with no change in voltage.

you say you did the cs144 alternator..and you have tested 2 other alternators, are they also the cs144 ?
can you take them into a shop/parts place for free testing.

You say noise gets louder and volts drop with the more they run...bearings ?

recently went through this on a non Toyota, voltage drop over time/distance regardless of speed. Ended up being a bad/loose cable.

I came across this article which might shed some light. Thoughts?

Alternators: Low Voltage To Battery