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-   -   Tundra electrical issues (http://www.risingsun4x4club.org/forum2/showthread.php?t=19937)

subzali 07-15-2013 09:21 AM

Tundra electrical issues
I guess it was only a matter of time :rolleyes:

A few weeks back my wife went out to start the Tundra and it was dead. I had her pull out the voltmeter and check the battery voltage and it was 0.8V.

When I got home I charged it with the FJ40 and started it up, then drove it to the auto parts store to have everything checked. He said my battery was a little low on charge but it was fine. Cranking Amps were down to around 500 from a CCA rating of about 700. Alternator checked out fine.

I went home, topped off the water in the battery and cleaned the terminals and greased them when I put everything back together.

It's been ok for the past couple of weeks except when I took a trip last week and it sat from Monday morning until Thursday morning. It was pretty slow to start. Overnight or over the weekend it has not really been a problem starting on Monday morning. Until the last week or so.

A few times now I've gotten in and turned the key to start and all the power is killed and the voltmeter on the dash drops to zero. So far the "fix" has been to open the hood, check the terminal voltage with a multimeter, which has ranged from 12.1-12.4V, and try starting it again. It starts up fine and is not an issue until it sits for a few hours again.

This morning I tried waiting for a few seconds and restarting it - as I waited the dome lighting and panel lighting slowly came back to life - and it kept dropping the voltmeter to zero until I gave in, opened the hood, checked the battery voltage again, and then it started up fine.

Should I just throw a new battery at it and hope it goes away? The battery was in the truck when I bought it 4 years ago so it could be aging, and by the cranking amps probably is. Or does it sound like a wiring issue?


DaveInDenver 07-15-2013 09:34 AM

Assume in your first sentence you mean 10.8V and not 0.8V.

You said the battery came with the truck 4 years ago and that it's a wet cell (standard) type. Wouldn't be surprised that it's in need of replacement. Might also just need the electrolyte replaced.

That they measured a reduction in the capacity would be a flag to me. How did they test it, was it a handheld device or a machine? To test a battery it must be under load and from what I've seen most times they don't adequately do this. Your starter is about the best load tester, slow cranking is a great warning indicator...

Still, I would check your cables first, looking for breaks at the terminals and make sure the ground terminal is solid on your engine block. The starting circuit is actually a good test because if the starter solenoid is engaged all the complex parts, computers, interlock switches, etc are working. The high current side of the starter is wired directly to the battery with a large cable and grounded by virtue of being bolted to the engine. There is a heavy cable that returns current to the battery.

I might suspect the solenoid contacts if it was just intermittent starting, but weird behavior in other places makes me less suspect of that. I'm not even sure the Tundra starter is built the same way as my old Denso start on the 22R-E, where the solenoid plunger arcs on the hot side contact and eats away to the point it no longer makes contact.

Open circuit, unloaded voltage doesn't really tell you much about the condition until the failure is major. You can judge overall condition with it but you need to be fairly accurate, the difference between 12.1V and 12.4V is important and you need the battery temp to be the same. If you think you've seen 12.1V after a good charge and it's fairly warm (but not super hot), then that would indicate the battery is not holding a charge well. I bet if you put even a relatively decent load, like the headlights, the battery voltage would drop significantly.

thefatkid 07-15-2013 09:38 AM

Sounds more like a loose or poor connection. When you say your greased the terminals, what did you use? Did you grease an then install the batter cables? Was there a bunch of corrosion prior to this failure?

Inspect all wiring very close. Check the main power wire to the fuse block (12mm on terminal and I think a 10mm inside the fuse block. A the next failure see if there is power in the fuse block with your volt meter (most fuses have a voltage tap on the back that you can touch to see if there is power).

A dead cell in a battery will not usually rear down to 0v. It is possible that you devolped a draw with the key off. Do you have any aftermarket radio equipment wired? Fridge? Does your volt meter have an amp setting?

subzali 07-15-2013 09:56 AM

Dave, thanks for the input.

I asked my wife to repeat the number to me, and she repeated 0.8V. I didn't check it when I got home (I don't remember) but I should have verified. I don't know how a battery can read that low and come back.

The 4.7L starter does have contacts that can be replaced if intermittent starting is a problem, but this is like my whole electrical system shuts off, so I think it's different. Maybe someone who's experienced starter contact failure on a 4.7L can chime in if it's similar.

Brian, I used some battery terminal grease in the little packet from the auto parts store, and I believe I put it on after I put the terminals on the posts. There was not a lot of corrosion, but enough that I decided to repaint my hold down bracket and pull the battery out and spray some paint under my plastic battery tray.

There are two aftermarket electrical items that I'm aware of in this vehicle: an aftermarket rear view mirror with compass and temperature indication, and an ASC sunroof installed by John's Sunroofs at Belleview and Santa Fe. Neither have ever seemed to cause any problems previously.

DaveInDenver 07-15-2013 10:06 AM

If it's truly 0.8V, then that actually points away from the battery as Brian points out. A completely dead, worn out battery will read like 10.5V to 11.5V. Those are batteries that beyond discharged and probably goners. That is something of an odd value for another reason, that's close to a junction drop. Not sure what could be big enough to flat a battery and still measure 0.8V without burning up, so I suspect that measurement might have been an error if all your connections turn out to be solid.

Dielectric or terminal grease is the right stuff. You can smear regular grease all over the terminals after you've made the connections, that's a good idea to prevent corrosion. But only conductive grease should be between the terminal and connector.

If there was corrosion around the battery it's possible the ends of the battery cables are corroded and partially broken. If you can, measure the voltage at the terminal of the starter, it should be within single digit millivolts of the measurement at the battery. IOW, with a DMM you should see 12.30V at the battery and maybe 12.29V worst case at the starter.

It's also possible the battery itself is broken, the plates inside are bussed together to the external terminal. Optimas, especially their side terminals, suffer mechanical breaks that cause them to open. With the Optima its often because people wire their winch to them but internally they are not connected with substantially large enough strips of copper and they melt open, literally like a huge fuse. Anyway, maybe the terminal is making intermittent contact. Measure with a voltmeter and twist and shake and bump the battery to see if the voltage drops out.

LXBRADY 07-15-2013 11:03 AM

Replace the battery.:ranger:

nakman 07-15-2013 11:32 AM

Did she have the meter clicked too far? Or maybe she was checking continuity instead of voltage? I dunno...

Put the 40 battery in the Tundra for a couple weeks and see what happens?

AHorseThief 07-15-2013 03:04 PM

The battery is old enough that if it were me, I'd just replace the battery and see what happens.

AxleIke 07-15-2013 04:33 PM

This happened to me on my 4runner. Dead one day, charged it. Did okay, and then dead again a few days later. New battery and its all good now.

subzali 07-22-2013 08:52 AM

So it's been working fine and I've been ignoring it. Parked it on Friday and went to start it this morning. Did the same thing.

Checked the battery right away, it read 11.9V but slowly climbed back up to around 12.15V at which point I tried again and it started right up.

Oh, and there was a little smoke coming from the negative battery terminal.

I think I'm going to get a new battery this week.

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