Battery Acts Dead but tests Good

[Silent D]

So first post, I did search and read for the last two hours can didn't find my problem.

I have a 2009 Tahoe LTZ, Canadian model, with stock battery. A few months ago, while driving all the interior power (lights, radio, etc) would turn off and the engine would die. I'd pull over and try to start it but it wouldn't, no slow crank-no click-noting at all. If I wiggle the + battery it would start. Then after a few months no issues at all. Now the last few months on occasions its been acting like it has a dead battery, slow to crank and won't start, volt meter reads 0-9 volts. I wiggle the + cable and nothing, jump start it and it fires up. While driving the volt meter reads about 15 volts charging. I had the battery tested at the dealer on the last oil change and they said the battery tested good with and without a load. I ended up putting it on a battery tender and the tender read 100% charged in about 15 minutes, no issues with it for a few weeks. I just took my wife to an appointment and while she was inside for about 20 mins the Tahoe was off and I listened to the radio. It wouldn't start when she came out so I got and jump and it fired right up. I went to Auto Zone and they tested the battery at 100% good and the alternator pushing 14.87 volts, and the charging system checked good as well.

There have been a few times when the wife was out with the kids and it wouldn't start for her. I can't have my wife and kids in a vehicle that might not start when you turn it off. Not to mention this is my tow rid for my boat.

Any ideas?

TIA,
Jason

 

[swathdiver]

Battery cables and or bad grounds. I'd still change the battery. We had a battery acting similarly last month and it was making me look everywhere else but at it even though it was the troublemaker!

Welcome to the forum!

 

[HiHoeSilver]

So first post, I did search and read for the last two hours can didn't find my problem.

I have a 2009 Tahoe LTZ, Canadian model, with stock battery. A few months ago, while driving all the interior power (lights, radio, etc) would turn off and the engine would die. I'd pull over and try to start it but it wouldn't, no slow crank-no click-noting at all. If I wiggle the + battery it would start. Then after a few months no issues at all. Now the last few months on occasions its been acting like it has a dead battery, slow to crank and won't start, volt meter reads 0-9 volts. I wiggle the + cable and nothing, jump start it and it fires up. While driving the volt meter reads about 15 volts charging. I had the battery tested at the dealer on the last oil change and they said the battery tested good with and without a load. I ended up putting it on a battery tender and the tender read 100% charged in about 15 minutes, no issues with it for a few weeks. I just took my wife to an appointment and while she was inside for about 20 mins the Tahoe was off and I listened to the radio. It wouldn't start when she came out so I got and jump and it fired right up. I went to Auto Zone and they tested the battery at 100% good and the alternator pushing 14.87 volts, and the charging system checked good as well.

There have been a few times when the wife was out with the kids and it wouldn't start for her. I can't have my wife and kids in a vehicle that might not start when you turn it off. Not to mention this is my tow rid for my boat.

Any ideas?

TIA,
Jason

Remove the battery cables, clean the connections. Reinstall with a little dielectric grease good and tight.

 

[Silent D]

Remove the battery cables, clean the connections. Reinstall with a little dielectric grease good and tight.

You think its something as simple as a bad connection? I pulled the terminal off the first time I did a battery tender charge and the terminals and posts were nice and clean, no corrosion.

 

[HiHoeSilver]

You think its something as simple as a bad connection? I pulled the terminal off the first time I did a battery tender charge and the terminals and posts were nice and clean, no corrosion.

It's an easy thing to do and either solve the problem or rule it out, so it'd be first on my list. Sometimes the cables will corrode or even break inside the insulation, too. You can ohm out the cables while wiggling them around and see if you get varied readings.

 

[Silent D]

Here are pics of each terminal. Nice and clean.

 

[HiHoeSilver]

Here are pics of each terminal. Nice and clean.

View attachment 196100 View attachment 196101

If the truck acts dead ( assuming the battery is good under load) but perks right up when you put jumper cables on it, then the power is not getting from the battery to the wire. Take the 15 minutes to put a light sand or wire brush on those battery posts and the inside of the clamps and see what it does.

 

[Larryjb]

When this happened to me, I went over every connection and still had trouble. It turned out to be a bad starter motor. Could be a bad spot on the commutator of the starter.

 

[HiHoeSilver]

When this happened to me, I went over every connection and still had trouble. It turned out to be a bad starter motor. Could be a bad spot on the commutator of the starter.

Could be. Next time it won't start, smack on the starter with a hammer while someone tries cranking it.

 

[Silent D]

So just cleaned the terminals. There wasn't any corrosion but the terminals and posts did have like a tarnish covering them.

I used some sandpaper and got the terminals and posts nice and shiny. I'll see if that makes a difference over the next few days.

I put the battery tender back on it too, to ensure a nice full battery.

 

[Silent D]

Could be. Next time it won't start, smack on the starter with a hammer while someone tries cranking it.

It doesn't act like a bad stater. Especially since it fires right up with a jump and showing low bus. I'll give it a go if it happens again after cleaning the terminals and posts though.

 

[ZACHBORIS]

It doesn't act like a bad stater. Especially since it fires right up with a jump and showing low bus. I'll give it a go if it happens again after cleaning the terminals and posts though.

I am no mechanic but wont a bad alternator sometimes cause similar problems?

 

[TahoeLTZ2012]

So just cleaned the terminals. There wasn't any corrosion but the terminals and posts did have like a tarnish covering them.

I used some sandpaper and got the terminals and posts nice and shiny. I'll see if that makes a difference over the next few days.

I put the battery tender back on it too, to ensure a nice full battery.

I believe some years had an issue with the cables and grounds. They looked clean on the outside, but if you cut open the terminal where the wire goes into the battery connector, there is corrosion. The voltage reads fine , but it limits the current. That when things start to not function properly.

 

[Silent D]

I believe some years had an issue with the cables and grounds. They looked clean on the outside, but if you cut open the terminal where the wire goes into the battery connector, there is corrosion. The voltage reads fine , but it limits the current. That when things start to not function properly.

I looked up the The Big 3 mod and would like to do that but holly hell that cable is $500 a spool. I'd love to keep this Tahoe for a long time but I do have some rust cancer on the left rear fender that is bubbling under the pain and I can see a rust color on the Diamond White paint. I'm not sure if its worth repairing or trading in when I get the amount owed lower. I'm also having an issue with the driver's side blend door for the a/c, its only allowing hot air through and the passenger's side heated seat doesn't work anymore.

I love the look of the new Tahoes and would love to get one I just owe too much on mine right now to be able to trade in. Mine has 104,500 on it and runs perfect, when the battery issue lets it start anyhow lol.

 

[Buzzcut]

Bad cell in the battery. Seen it alot over the years

 

[Silent D]

Bad cell in the battery. Seen it alot over the years

Even if it tests good? Scanner said "Good" "100%"

 

[kbuskill]

Replace battery cables and consider it fixed.

 

[Silent D]

No issues at all today. Hopefully cleaning the terminal and posts did the trick. Time will tell.

 

[kbuskill]

No issues at all today. Hopefully cleaning the terminal and posts did the trick. Time will tell.

Removing the terminals from the battery to clean them probably broke up some the corrosion inside the cables to allow better transfer of current but my guess is it will return to its previous state.

For your sake I hope I am wrong but there have been WAY to many of these trucks with the same issue and it is the cables 99% of the time.

 

[Buzzcut]

Even if it tests good? Scanner said "Good" "100%"

Unless they did a true load test it’ll check good every time.
YMMV



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