Electrical issue... grounding? short?

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nosole

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I'll try to provide as much info as I can, but I'm completely stumped with a electrical issue on my '04 Suburban 1500 that prevents me from starting the truck (or any electrical response now).

I've had an problem with what I thought was a bad ground where the truck will be functioning fine, then I'll park it, step away for a minute, hop back in, and when I try to start it, it won't start. It'll sometimes click a bit, sometimes try and fail to turn over, or get minimal current with the gauges fluttering and dash lights flickering. This typically happens 2-3 times a year. The battery is fully charged and healthy. To solve the issue in the past, I disconnect the ground from the batter to clean off any corrosion from the cable end and reattach. Sometimes it works the first time. Sometimes I have to fiddle with it a bunch of times until I can get a solid connection, but it's always been correctable and the problem will disappear for a number of months.

A couple days ago though, I ran into the same issue, but was unable to correct it as I had in the past. I removed the rubber boot from the stud/contact and gave it and the battery terminal a thorough cleaning, but the problem persisted. I checked the battery and it was showing normal (12.4V) touching the multimeter lead to the battery terminal, but when I screw in the stud and take my reading touching it, it only reads 4.5-5V.

I was able to get a jump, but it took a few tries. Inititally, it struggled to turn over, but eventually I was able to get it started by tapping the starter (which appeared to be seizing a bit) while starting the ignition. At that point, I drove home, and as soon as I parked it and turned the ignition off, it instantly died. No running lights, no interior lights, etc.

I have since replaced the ground cable altogether, but am running into the same issue. Still no electrical response. Normally, when attaching the ground cable to the terminal, I'll get a few small sparks per usual, but now there is nothing. The battery is still normal (12.4V), and even with the new cable, I get the same reading as above (4.5V) when touching the multimeter lead to the ground stud. Leaving all cables connected overnight yielded no change, as in, no battery discharge, but still no electrical response in the truck. One small thing is that cigarette outlet still shows power for my phone charger (though I haven't taken a reading with the multimeter).

What can I look into next?
 
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Fless

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Sounds like a bad or intermittent cell in the battery. How old is it, and have you had it load tested?

One thing I don't understand is, what contact points are being used when you read the 4.5v? And is the battery connected to the truck then, or not?
 
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nosole

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Sounds like a bad or intermittent cell in the battery. How old is it, and have you had it load tested?

One thing I don't understand is, what contact points are being used when you read the 4.5v? And is the battery connected to the truck then, or not?
No, I haven’t had it load tested.

The battery type for this truck has female terminals on the battery. So the cable ends have a bolt (which I’ve been calling “stud”) that attaches to the battery. When I get the 4.5 V reading, it’s when the multimeter lead is touching this stud screwed into the negative terminal. I get the same reading from the bolt regardless of the ground cable being connected or not.

The battery isn’t very old. I’ve had it now for 3+ years, but when this issue first showed up, the battery was one year old, at most
 

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Side post battery terminals. You can get new bolts for them, but I think there is either a bad terminal connection or, more likely, a defective battery.
 

afpj

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I get the same reading from the bolt regardless of the ground cable being connected or not.

Wait, you get 4.5 v by touching the meter from positive terminal of battery to negative cable without the negative cable connected to the battery? I didn’t understand that statement.
 

rockola1971

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12.4v is not "normal" for a fully charged 12v automotive battery. It should be closer to or over 13v. Your alternator puts out 13.8v plus.

If you are reading 4.5v across your battery with no load attached then you have shorted cell(s) in your battery OR the battery isnt getting charged by your alternator OR there is something loading your battery down. (likely the BCM) because of a bad ground.

Disconnect the battery, fully charge it, then let it sit for 4-6hrs and measure the voltage of the battery. If its below 12.6v after a full charge then the battery is bad.
 
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nosole

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Wait, you get 4.5 v by touching the meter from positive terminal of battery to negative cable without the negative cable connected to the battery? I didn’t understand that statement.
Correct. But as I’m standing here now, it’s no longer doing that. Here are the readings I’m seeing now…

Battery disconnected, touching terminal (12.3V)
AB398EE3-ED4F-409F-BC44-1AC0A977EB37.jpeg

Battery connected, touching bolt, ignition off (8.3V)
EAD3DD5B-3168-4B5F-A568-D577E08C047B.jpeg

Battery connected, touching bolt, ignition on, engine not running (5.4V)
D263C79D-E598-4527-8933-843084277262.jpeg
 
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nosole

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12.4v is not "normal" for a fully charged 12v automotive battery. It should be closer to or over 13v. Your alternator puts out 13.8v plus.

If you are reading 4.5v across your battery with no load attached then you have shorted cell(s) in your battery OR the battery isnt getting charged by your alternator OR there is something loading your battery down. (likely the BCM) because of a bad ground.

Disconnect the battery, fully charge it, then let it sit for 4-6hrs and measure the voltage of the battery. If its below 12.6v after a full charge then the battery is bad.
Roger that. I’ll give it a full charge, take new readings and report back.

On a related note, I replaced the alternator (with OEM AC Delco) in March last year.
 

rockola1971

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Correct. But as I’m standing here now, it’s no longer doing that. Here are the readings I’m seeing now…

Battery disconnected, touching terminal (12.3V)
View attachment 363203

Battery connected, touching bolt, ignition off (8.3V)
View attachment 363204

Battery connected, touching bolt, ignition on, engine not running (5.4V)
View attachment 363205
Assuming the 8.3v reading is valid then you have something loading your battery down in your electrical system and thats why your battery voltage is so low. Start puling fuses one by one and see which one cause the voltage to jump up to 12v+. Then you are troubleshooting that branch circuit to see what is likely shorted to ground.
 

Doubeleive

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Assuming the 8.3v reading is valid then you have something loading your battery down in your electrical system and thats why your battery voltage is so low. Start puling fuses one by one and see which one cause the voltage to jump up to 12v+. Then you are troubleshooting that branch circuit to see what is likely shorted to ground.
Doubtful it would take a pretty severe short to make that happen and one of the cables would be warm to the touch, I would lean more towards a bad battery.
 

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