Bad battery or bad alternator? (1 Viewer)

MJK

Joined
Mar 13, 2020
Messages
470
Location
Tucson
It seems like sometime over the past couple years batteries went from lasting me 8-10 years to half that if I am lucky. I'm on my 3rd pair of batteries in less than 5 years in my diesel pickup. Anyways, all that b/s and the parts store drama associated with it is part of what encouraged me to buy an Autel AL539B. It is an OBD scanner, voltmeter, and does battery load testing (giving you actual vs rated CCA). It also has a vehicle start test that monitors voltage drop under load. It is a pretty handy thing to have with you and takes the guesswork out of 'good battery' or not. I charge suspect batteries (CTEK has a reconditioning cycle), test them on the Autel, and then haul them to the parts store for replacement. So far their testing results have matched mine (after more than a little griping).

I have not had this problem on the LX, although the alternator does not seem to charge beyond 13.2-13.3V at idle. If and when it finally kills itself I'll be looking for an OEM rebuild and checking all the high current wires carefully.
 
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Joined
Oct 23, 2014
Messages
103
Location
San Jose, CA
So, I havent had a chance to mess with the car; I was busy most of sunday with the family and didnt get to it last night. I did hook the battery up to my noco 3500 'smart' charger and used the 'reconditioning' mode to let it charge up to full. That charger shows it at 100% now. Current battery voltage is 12.91v. ALso, i do plan on replacing the battery just in case... i have read that deep discharging those batteries is quite bad for them. Not sure if reconditioning helped but i mostly did that because i had the charger and the time. Will throw the battery back in it today and check the charge voltage when running and under load. Might see about pulling the alternator tonight as well to inspect the brushes.

I did order a new 100a alternator from densoproducts.com, however they called me and told me they are on backorder and they didnt expect to receive them for 30-90 days so I cancelled my order. Same story with the 130a sequioa alternator. I think i can get a 100A alternator directly from toyota (~$200 w. core fee + shipping), however I have heard mixed reviews on their rebuilds. The later model land cruiser alternators (with the 4 pin connectors, 130A) are in stock at densoproducts (also around $200).

Will the late model land cruiser alternators bolt in place of my current one? (i know i will need to swap the connector or use a pigtail to get it to work).

I have heard of a lot of people switching to the sequioa alternators instead of the later model LC ones, but i believe that was due to the sequoia parts being new and not reman; seems like that new units are no longer available (at least from any of vendors i have checked, havent seen what toyota sells at the dealer).
 
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Joined
Oct 23, 2014
Messages
103
Location
San Jose, CA
So i had a chance to hook the battery back up to the truck and see what happens when i spin it up:
Battery disconnected: 12.91v
Battery connected, ignition off: 12.88v
Ignition on, high beams on, Interior fan on Hi: 11.7v
Running, at idle: 11.86v

Was able to start the truck fine. I revved the truck up to 3K RPM and didnt see the voltage indicator on the dash move at all, it was sitting just above the mid way mark (I assume thats 12v, but its not marked). I wasnt able to take a reading with rev's, only look at the gauge on the cluster. I assume this is a bad alternator based on those readings. I also did check the battery connectors per Slee and they seemed tight. voltage was measured on the stainless extensions for all tests.
 
Joined
Oct 23, 2019
Messages
369
Location
Western Australia
So i had a chance to hook the battery back up to the truck and see what happens when i spin it up:
Battery disconnected: 12.91v
Battery connected, ignition off: 12.88v
Ignition on, high beams on, Interior fan on Hi: 11.7v
Running, at idle: 11.86v

Was able to start the truck fine. I revved the truck up to 3K RPM and didnt see the voltage indicator on the dash move at all, it was sitting just above the mid way mark (I assume thats 12v, but its not marked). I wasnt able to take a reading with rev's, only look at the gauge on the cluster. I assume this is a bad alternator based on those readings. I also did check the battery connectors per Slee and they seemed tight. voltage was measured on the stainless extensions for all tests.
Yeah the LC battery readings are a little low but not that bad I think. Check the youtube videos showing how to diagnose battery, alternator etc

If its your alternator I think you can test the alternator points with a multimeter, that would have to give you evidence enough.
 
Joined
Oct 23, 2014
Messages
103
Location
San Jose, CA
Update- Finally got the new alternator in today and put it in, 14.2v with the headlights and stereo on. I also threw a Odyssey battery into the truck. I tore down the old alternator and looked at the brushes and they seemed to be in OK shape. The rectifier on the other hand looked burnt up. I also noticed a rattling sound when spinning the alternator that turned out to be a piece of solder. Looks like the diode overheated and melted some solder in the alternator.
 

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