Battery or Alternator?

[ChrisA]

The Tundra was left stranded at work yesterday. It made a trip from Richmond, VA to DC on Saturday with a lot of stop-n-go on I-95 during the return trip. It did notice it turned over a little weak on one stop when I got back to town. I didn't drive it on Sunday. Monday morning the start was noticeably weaker, but it did start. Yesterday after work it wouldn't turn-over at all; just the clicking sound of the starter. The battery is 6-yrs old. Does this sound like the battery or sound like the alt died and stopped charging? Would hate to buy a new battery if I got a year or two left in this one, or kill a new one with a bad alt. Haven't found a ride in yet to check things out with tools at hand.

[Highwaylizard]

Sounds like a dead battery but you should be able to take it in somewhere like Auto Zone and have it tested for free.

[DMZX]

Charge the battery and start the engine. Put a volt meter on the alternator to see what it is putting out. It should be more than 14 volts. If it is much less than that - weak alternator. If it is not - bad battery.

[GEE-BEE]

Mine was dead with 39k mikes, age as the plates sulfate and ground it out

Installed a 1800 amp kineticwith a cnc mount from artec...

I did remove the stock battery tray and make a new plate for the knietic, same price as going with a sears platinum

powder coated the mount, and new wiring...

GB

[Remmy700P]

6 years. It's time. Replace the battery. I suggest the Duralast Gold 24F-DLG from AutoZone. Go here for a review thread: went shopping for a 27F battery today (results inside)

[UPbuilder]

Your battery will drain quicker than that with a bad alternator, my bet is on the battery. Sounds like it's not taking much of a charge anymore, and 6 years is a pretty average life.

[ChrisA]

Picked up a new Deka Gold?? I've been using one of their small AGM batteries in my racecar for a few years now. No idea how this will hold up. Truck started up and I was seeing 14.75v at the battery terminals with no excessories turned on.

[Highwaylizard]

6 years. It's time. Replace the battery. I suggest the Duralast Gold 24F-DLG from AutoZone. Go here for a review thread: went shopping for a 27F battery today (results inside)

That is what I got and no problems at all so far. Only had it a year but the truck had the OEM battery in it up until last year.

[italiantundra88]

also if you go to autozone i got a link to a coupon thread for autozone in my sig. i think right now i got one that is still valid for 10 off 50 and 20 off 80

[ChrisA]

Charge the battery and start the engine. Put a volt meter on the alternator to see what it is putting out. It should be more than 14 volts. If it is much less than that - weak alternator. If it is not - bad battery.

Okay when you say put a volt meter on the alternator do you mean at ITs' terminals or at the batteries terminals? I can't even see were the Alt's terminals are located. At the Batt when first installed it showed over 14v with no accessories on, after the drive home the batt. was at 13v engine off and 13.55v engine on. With air on high and bright lights it dropped to 13.35v.

[ChrisA]

Deleted double post

[DMZX]

Okay when you say put a volt meter on the alternator do you mean at ITs' terminals or at the batteries terminals? I can't even see were the Alt's terminals are located. At the Batt when first installed it showed over 14v with no accessories on, after the drive home the batt. was at 13v engine off and 13.55v engine on. With air on high and bright lights it dropped to 13.35v.

Chris,

I started my truck and put the voltmeter on the battery terminals. I got 14.32 volts. I turned the engine off and metered the battery. I got 12.24 volts. This was with nothing on. I tuned on the headlights, fogs, and fan and still got 14.27 with the engine running.

This tells me that my alternator is healthy, as is my battery. BTW. my alternator has 102,000 miles on it and I replaced the OEM battery last month (7 years old)>

I do know that when a battery gets weak the alternator can wear and weaken from the additional load put on it as it tries to keep up with the slowly dying battery.

13.55 volts with the engine running seems a bit weak. 12 volt alternators (in my experience) produced over 14 volts even under load.

Edit/update - After sampling of 5 automotive forums with the question of "alternator output at idle," the consensus was 13.5 -14.5 volts. So I think you good to go.

[Remmy700P]

Output voltage is dependent upon temperature as well, so keep that in mind...