Bad battery or bad alternator? (1 Viewer)

Joined
Oct 23, 2014
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San Jose, CA
I had an interesting day today. Started off with a 30 mile drive, mostly freeway, out to go on a hike with the family. After a hour and a half hike, jumped back in the truck, drove a short distance (100 yards), turned the truck off, got the kids situated, started up and drove off. We decided to check out where a road went and traveled another 5 miles or so on a windy back road.

All of a sudden my aftermarket radio started acting like i had poor reception which was strange because my phone was plugged directly into it playing music. I pulled off to the side of the road and the radio died. When trying to figure out what was going on there the engine died. I immediately assumed alternator as I have heard this is a typical symptom. I went ahead and tried to start the truck and got nothing. Turned the key off then back on and I got a warning buzzer, the battery light, ABS light, traction light, etc. but no clicking like the starter was trying to catch. I went into the back and got my jumper battery and a cheap multi-meter i keep in the trunk and tried to figure out what was happening. I measured the voltage before I started it and i seem to recall it was in the 6v range. I jump started the car with the jump pack (btw, just got the antigravity battery jumper and it worked great) and the engine fired right up. I went back and checked the voltage and it was showing something like 8v. The truck ran for maybe 30 seconds, started to hiccup and then died (no buzzer or other lights were noticed but I didnt stick around in the cab very long). I then had the truck towed home. Note- i didnt notice anything weird other than the radio acting up immediately before the truck died. I also didnt hear any grinding noise (bearing noise) when it was running.

This evening (7 hours later), i went back out to the truck and pulled the battery to charge it up so I can drive it into my driveway when I'm ready. I decided to use my nicer voltage meter to see where the battery was sitting and it registered just under 12v (something like 11.8v). I attempted to start the truck and this time it clicked like the starter solenoid was trying but no go. Dash lights seem normal (no buzzer). Interior lights were replaced with LEDs and those seem to work fine, also the electronic door locks are also working fine. I verified the voltage with my cheap meter and it matches my nice meter so I have no reason to suspect the earlier very low voltage readings. Battery is currently on a charger (btw its an interstate lead acid 'normal' battery).

I dont know why the battery would have rebounded like that, perhaps someone on here would know? I would like to fix it myself as we are (trying) to avoid any contact with other people due to covid.

In summary:
Truck drove 35 miles on the highway with multiple starts along the way - no issues.
Truck radio died, then the engine died. Jumping the truck worked but then died ~30sec later.
Prior to jumping battery showed 6v, while running after jump battery showed 8v.
After a tow home and it sitting for 7 hours, battery shows 11.8v (still doesnt start, didnt try jumping it).

I should mention it was rather hot today, 95-100F where we were at. Right now temp is ~80F.

Thanks!
 
Joined
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Magna, UT
Start by checking your battery cable connections. I'd almost bet on that being your issue. (or if not, it's a contributor and a free fix)
 
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Get the battery charge first and get the vehicle started now check voltage at the battery you should have no less than 13.5 volts if you have clamps on your VM that would be best get the vehicle to idle and turn on every accessories you have on the vehicle (High beams, Blower on High etc.) then bring up the rpm's around 1500 and see what is your charging voltage. If your charging voltage stays above 13.5 your alternator should be ok another thing you can do is let it idle and remove the negative cable from the battery while running vehicle should not die at this point if it does stall your alternator may be weak.
 
Joined
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San Jose, CA
Battery connections were replaced with SLEE replacement connectors (they heavy duty military versions with the stainless steel extensions) several months ago. I also coated them with battery anti-corrosion spray and didnt see any issues (no visible corrosion) I haven't checked the ground points thoroughly yet, however eyballing them they are intact and dont have any obvious issues.
 
Joined
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Get the battery charge first and get the vehicle started now check voltage at the battery you should have no less than 13.5 volts if you have clamps on your VM that would be best get the vehicle to idle and turn on every accessories you have on the vehicle (High beams, Blower on High etc.) then bring up the rpm's around 1500 and see what is your charging voltage. If your charging voltage stays above 13.5 your alternator should be ok another thing you can do is let it idle and remove the negative cable from the battery while running vehicle should not die at this point if it does stall your alternator may be weak.
So, assuming I'm able to charge the battery up and get the truck running with full load like that, if the alternator checks out that would likely be the battery, correct? I just cant understand why I had such low voltage.
 
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So, assuming I'm able to charge the battery up and get the truck running with full load like that, if the alternator checks out that would likely be the battery, correct? I just cant understand why I had such low voltage.
If you can charge the battery to at least 12.5v you should be able to start, how old is your current battery? Most battery last 3-5 years, I have good luck with Toyota batteries all my Toy's have Toyota batteries one of them is almost 8 years old and the last battery in my truck lasted 9 years.
 
Joined
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Did the battery discharge completely in the last severel/few months
Other than sitting more than usual due to the current situation, it hasnt been deep discharged. After sitting for a while at one point it did seem to struggle a bit to start, but it did not require a jump.
 
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Western Australia
Other than sitting more than usual due to the current situation, it hasnt been deep discharged. After sitting for a while at one point it did seem to struggle a bit to start, but it did not require a jump.
Does it take a couple turns every time after sitting a while. I bet it will be dead soon, new battery. I got a new alternator a long time before this type of behaviour started with my battery. How old is the battery? sounds like its on its last legs.
 
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If you can charge the battery to at least 12.5v you should be able to start, how old is your current battery? Most battery last 3-5 years, I have good luck with Toyota batteries all my Toy's have Toyota batteries one of them is almost 8 years old and the last battery in my truck lasted 9 years.
Battery is dated 6/15 so it sounds like its about 5 y/o.
 
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Does it take a couple turns every time after sitting a while. I bet it will be dead soon, new battery. I got a new alternator a long time before this type of behaviour started with my battery. How old is the battery? sounds like its on its last legs.
No, only that one time and that was after about a month of sitting. This morning the truck started no issues after sitting for ~ 2 weeks (i had started the truck a couple of times the other day but only let it run for a few minutes so no charging was happening)

For the record; I think ill replace the battery no matter what, mostly for peace of mind. I am trying to determine if I also need to do the alternator at the same time.
 
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I say it's time for a battery, one or more of the cell is dead. Another way you can load test your battery is make sure you have at least 12.5v or higher, hook up your VM and turn key to run position engine off now turn on high beams and blower on high let it run for about 30 sec. and then look at your battery voltage as it recovers it should be close to what you started when it comes to rest.
 
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Battery is dated 6/15 so it sounds like its about 5 y/o.
For me, its winter here, thats when the battery really starts to be effected by weather and depletes. You can take it for a long drive and charge it back up, or charge it with a good charger. Either way, 4 years is what the shop says is the turnover average of batteries. You got about the same as me ~5 years so you did well.

My new Supercharge battery does the job, I will be getting a 15amp Projecta solar controller soon and atleast a 100W solar panel on the roof to charge it. Already ordered the Projecta charge controller, it does 14.9V charge rate to calcium (sealed) starter battery. That should solve the Alternator problems with undercharging the calcium battery. Another issues with these Alternators only charging about 14.2V
 
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If you're only using the car twice or so a week, it will need a full charge every so often. Shop recommended at least once every 2 months I think.

That's why I'm getting a charger, so it charges while car sits out the front. Higher Watt panel ensures it will be fully charged all the time.

Just want to milk every cent out of my battery purchase @ $220 they not cheap.
 

suprarx7nut

The YotaMD Guy
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Alternator gets my vote. I'm all too familiar with dead alts on a 100. While driving, the battery shouldn't be able to kill the engine. That's the work of a dead alternator. I think your alternator has died and allowed your battery to go flat and now you're having a hard time getting that battery back to life.

Charge up that battery overnight. Make sure your charger is a full charger and not just a trickle charger. If the battery hit 6V or less, it's likely damaged and will need a reconditioning cycle from a nice charger or just flat out replacement.

I've had dead alternators pass the parts store in-car tests, so I wouldn't put much weight on those. If the car's running and your output voltage to the battery isn't somewhere north of ~13.3-13.4V, I'd say the alternator needs replacement. It's good PM, since you're really SOL if it dies on a road trip (like it has for me twice in the last 5 years...).
 
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Alternator gets my vote. I'm all too familiar with dead alts on a 100. While driving, the battery shouldn't be able to kill the engine. That's the work of a dead alternator. I think your alternator has died and allowed your battery to go flat and now you're having a hard time getting that battery back to life.

Charge up that battery overnight. Make sure your charger is a full charger and not just a trickle charger. If the battery hit 6V or less, it's likely damaged and will need a reconditioning cycle from a nice charger or just flat out replacement.

I've had dead alternators pass the parts store in-car tests, so I wouldn't put much weight on those. If the car's running and your output voltage to the battery isn't somewhere north of ~13.3-13.4V, I'd say the alternator needs replacement. It's good PM, since you're really SOL if it dies on a road trip (like it has for me twice in the last 5 years...).
Yep, these cars should really have it replaced at their age. However, you can still drive the car with dead alternator. The A/T temp light will come on, which will confuse the hell out of you and your mechanic no doubt, but the way to tell. Pray you have a mate with jumper cables :)
 

sleeoffroad

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Battery connections were replaced with SLEE replacement connectors (they heavy duty military versions with the stainless steel extensions) several months ago. I also coated them with battery anti-corrosion spray and didnt see any issues (no visible corrosion) I haven't checked the ground points thoroughly yet, however eyballing them they are intact and dont have any obvious issues.

Make sure the large 3/8 bolt that attaches the terminal extension to the terminal is tight. We have seen those losen up and cause bad connections and arcing between the extension and terminal. When measuring voltage do so on both the extension piece and terminal to ensure that you check that charge voltage gets to the battery.
 
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Make sure the large 3/8 bolt that attaches the terminal extension to the terminal is tight. We have seen those losen up and cause bad connections and arcing between the extension and terminal. When measuring voltage do so on both the extension piece and terminal to ensure that you check that charge voltage gets to the battery.
Ill check it out.

Given that the alternator is ~$150 i might just throw a new (denso reman 100a) on there... Is it worth it to try and upgrade to a 130a unit from a later model 100 or a Sequioa? I have a winch and have plans to add more lighting in the future.
 

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