Feint Battery Charging System Light

[CutthroatSlam]

Alternator went out on the 2014 4Runner, stranding my wife in Mackay, Idaho (population ~500). Original alternator went 318.5K miles. I replaced with new Toyota Denso alternator and that lasted to 395.7K miles, or about 78K miles. Replacement alternator (do not know if it was new or reman, but it was $332) arrived late Monday and the local mechanic it in and sent her on her way. She made it to our Montana home late Monday night, with no further issues. However the battery charging system light remains feintly lit as shown in the following before and after pictures. Not sure what could be causing this?

 

[AuSeeker]

Check the voltage with it running and also when it's off, running should be close to if not a little above 14V, off should be around 12.75/13.5ish.

 

[spartacus]

Wouldn't hurt to check battery terminals and and alternators connections are good and tight also the serpentine belt is snug.

 

[Humble Leader]

in order of my best guesses:

- the alternator itself just isn't that good. maybe it is remanned, maybe not toyota. that's where I'd start. maybe it's not putting out the right amount of voltage. a faint light would mean this could be a cause
- then move onto wiring. corrosion, poor ground etc. will cause voltage drop
- lastly the belts

given you didn't get much life out of the second alternator I'd place bullet 2 ahead of bullet 3.

 

[CutthroatSlam]

Update: with about 1,000 miles of driving, this feint light has reportedly (from my wife) gone dark.

 

[Humble Leader]

Update: with about 1,000 miles of driving, this feint light has reportedly (from my wife) gone dark.

curious to see when you get the vehicle what the voltage output is at idle. maybe the old alternator didn't charge the battery fully, it was weak and thew new alternator had to work at max capacity to charge that battery

if you have repeated checks at 14.5v when car is running over a period of days I think you can call it resolved

 

[CutthroatSlam]

curious to see when you get the vehicle what the voltage output is at idle. maybe the old alternator didn't charge the battery fully, it was weak and thew new alternator had to work at max capacity to charge that battery

if you have repeated checks at 14.5v when car is running over a period of days I think you can call it resolved

She starts the drive from Montana to SoCal either Wednesday or Thursday. I’ll be checking it over the weekend. The battery is new as of September, but was on the old Denso alternator until it failed. So yeah it could have not been fully charged, but it never had issues starting the truck.

 

[CutthroatSlam]

Finally got around to testing with the voltmeter. I get 13.92 volts at idle and at 2,000 rpm.

I noted that the very feint charge light slowly come on the same speed as the gauge illumination.

 

[Humble Leader]

interesting. alternator is basically charging to spec. 13.9v is pretty typical for these 4runners. maybe just a tad under the 14v. could that be the faint light cause? maybe. or perhaps one of the internal diodes that converts AC to DC is just not working like it should. causing the computer to be confused and maybe throw a dim light. aside from checking all the ground connections and wiring , throwing a new alternator in to test would help you narrow fairly quickly. I guess you could swap the alternators between both 4runners and see what happens

 

[CutthroatSlam]

Here’s a pic from today taken because the vehicle rolled past 400K miles, but it shows the feint charge light:

 

[CutthroatSlam]

Comment from TheTruckStop.us forum was to set the multimeter on ac and test the battery side lead at the alternator for ac. They too suggested it could be a bad diode.

P.S. I would just buy a Denso alternator from Toyota before I would attempt swapping alternators between our two vehicles.

 

[CutthroatSlam]

Update:

Sent an e-mail describing the issue to our local mechanic who thought it was likely the alternator, but first check the wiring connections at the alternator and the battery, which were fine.

Next pulled the paperwork from the mechanic who installed it. It was an Ultima 130 amp alternator from O’Reilly’s, so it has a warranty on it. Took the vehicle to O’Reilly’s in Missoula and described the problem. They brought out their alternator tester, connected it and had me start the vehicle. It tested at 14.1 volts, so it was charging. All diodes passed. Voltage regulator passed. Alternator is doing what it’s supposed to do, but no explanation for the feint charging light.

I have a replacement brush arriving for the original Denso alternator. I will install that into the Denso alternator. Thought I would swap the Denso alternator back in, but the tests have me feeling more comfortable and we’ll just keep the Denso as a spare back up.

 

[CutthroatSlam]

Update: Discussed the feint charge light and the sporadic no-start with my local mechanic on our loop road (he’s very good and wants to hire me when I retire, but I will only work on my cars). He said the no-start pointed towards issue with the starter. So I ordered new Denso Starter and Alternator from dealer while they still had their sale going on and free shipping.

I had to return to work in SoCal, so I left the parts with my wife who took the 4Runner in. I also provided a list of things I wanted him to check while he had it up on the lifts.

Starter had a corroded cable and a broken bolt. The corroded cable was the likely cause of the feint charge light and the sporadic no-starts. With both the new starter and alternator in, the charge light is now officially OFF!

Bushings on the lower control arms are worn. I already have a new set of OEM upper and lower control arms to install and will get on that when my wife is next down in SoCal with the 4Runner sometime in mid-February.

Confirmed my observation the rear shocks are leaking. These are Bilstein 5100s with just over 300K miles on them. New ones ordered and wife will bring those down for me to install.

The 2014 now has 407K miles and just experiencing the normal expected wear on parts. I call this the needy phase of life. Engine is still running strong with no issues or leaks, but I’m anticipating the water pump will be next to go.

 

[02SE]

I'm just now seeing this thread, and noticed the problem was poor continuity due to a corroded cable. Usually when something like this happens it's a poor connection, or corroded wiring itself, or both. I'm glad it was figured out.

Oh, and it's killing me so I have to say the word is 'Faint'.

'Feint' is like a pretend punch in boxing.

 

[CutthroatSlam]

Thanks for the clarification on word usage. I’m usually pretty good on this, but this one got me. Should have used dim instead.

 

[Humble Leader]

I'm just now seeing this thread, and noticed the problem was poor continuity due to a corroded cable. Usually when something like this happens it's a poor connection, or corroded wiring itself, or both. I'm glad it was figured out.

Oh, and it's killing me so I have to say the word is 'Faint'.

'Feint' is like a pretend punch in boxing.

haha no no feint was actually the right word. it's a fake out. dims , gets a bit brighter, dims again, the punch is the full brightness, the every so slight dim is a fake out "get ready for it, Im gonna light up full blast, might be today, oh no, maybe tomorrow. sike"

 

[1000MPH]

Thanks for this thread, good stuff to keep in mind.
My rear 5100’s leaked and I replaced at 6 years/ 60k. They were still in working condition but obviously lost a bit of fluid. I wish they would paint them, they get so corroded after less than a year.

 

[CutthroatSlam]

This 2015 4Runner stays out west and roams between homes in Southern California and Southwest Montana, so it does not experience the problems of the rust belt. The Bilstein 5100s do not suffer corrosion problems. I’m hopeful that I do not need to cut the cams in the lower control arm to remove them, but did buy some cams just in case. Seems like all the problems on the lower control arm bolts and cams are on vehicles in the rust belt areas of the country, so fingers are crossed on this upcoming job.