Truck Died Last Night on a Main Thoroughfare, replacing batteries in 2 hrs or so, what may be needed? (Details in thread)

[tjk]

My truck wouldn't start at the auto parts store when the batteries were bad. All lights started flashing, transmission warning etc., it would even jump start with the NOCO. The only solution was to disconnect the N1 for 30 seconds and then it started right up with the NOCO. When I replaced the batteries, I only disconnected the battery terminals. Nothing else and it worked without any warning lights or any other problems.

Isn’t N1 under current when everything is connected?

Sponsored

 

[tjk]

Make sure your fender ground is disconnected, your IBS connector is disconnected, and all other disconnected ends are isolated from each other and ground. Install fully charged batteries. Reconnect the battery cables on the batteries. Reconnect the fender ground . Reconnect the IBS connector.

When you say the fender ground, are you referring to the black main battery terminal?

 

[MudderNuker]

Isn’t N1 under current when everything is connected?

Possibly but it didn't cause any issues when I swapped the batteries.

 

[sharpsicle]

Sounds like a blown fuse somewhere. Known to happen when replacing batteries if you don't disconnect everything in just the right order.

 

[WILDHOBO]

wish I had read this earlier, I did the AUX battery first (positive, the neutral) then the N1 connector on the fuse block, then the main battery (positive, IBS, neutral). The truck started, about to drive it about 2 miles home. Still some lights on the dash, but I’m hoping they resolve as the truck adjusts to its new batteries.

I didn’t get that complicated. I first disconnected all cables at the main battery and isolated them from each other with welding gloves. Then I removed the old main battery. Then I removed and replaced the aux battery. Then I replaced the main and reconnected all cables. No issues whatsoever. No dash messages at any point.

 

[Lost1wing]

The truck starts up no problem, but it’s reporting only 11.8v on the on-board system. Both batteries are brand new, I only had time to charge the big battery as high as 80%+ using the following:

https://www.harborfreight.com/autom...ocessor-controlled-battery-charger-56796.html

Get a vom and measure your fuse array terminals with the engine running.

 

[Lost1wing]

When you say the fender ground, are you referring to the black main battery terminal?

When people pull the main terminal off of the main neg post, they assume all is dead. Unless you remove the main cable from either the top plate above the ibs or at the fender, the aux is still powering the vehicle. Bad things happen when this assumption is made. That message you got is saying that bad things happened, especially if you just replaced the batteries.

By measuring the voltage at N1, N2 N3 and N7, we can see a bit more of the story.

 

[tjk]

When people pull the main terminal off of the main neg post, they assume all is dead. Unless you remove the main cable from either the top plate above the ibs or at the fender, the aux is still powering the vehicle. Bad things happen when this assumption is made. That message you got is saying that bad things happened, especially if you just replaced the batteries.

By measuring the voltage at N1, N2 N3 and N7, we can see a bit more of the story.

To clarify what you want, hook up my voltmeter to each of those posts with the red with the black lead going to the main ground?

 

[MudderNuker]

The truck starts up no problem, but it’s reporting only 11.8v on the on-board system. Both batteries are brand new, I only had time to charge the big battery as high as 80%+ using the following:

https://www.harborfreight.com/autom...ocessor-controlled-battery-charger-56796.html

Have you checked to make sure the charger is on AGM mode? Fully charged I think it should be at 12.8v.

 

[tjk]

Have you checked to make sure the charger is on AGM mode? Fully charged I think it should be at 12.8v.

Indeed I did switch it to AGM mode.

 

[ShadowsPapa]

Charge the batteries OUT OF the truck. Charge before installing.
If you ever have to charge the batteries while they are in the truck, such as with a battery tender, always make sure you connect the negative of the charger to the top of the IBS and never directly to the battery terminal below the IBS.

Ideally, you charge both batteries even when replacing only one, and do an IBS reset at that time.

If N7 or N3 of that high current fuse array are blown, you have issues.
N7 is how the alternator connects to the batteries - if that's blown, they can't charge and it will read only battery voltage which will be low.
11.8 is pretty much a dead battery - or, it means the truck is running off the batteries and pulling the voltage down low.

 

[Lost1wing]

To clarify what you want, hook up my voltmeter to each of those posts with the red with the black lead going to the main ground?

Yes

 

[tjk]

W

Charge the batteries OUT OF the truck. Charge before installing.
If you ever have to charge the batteries while they are in the truck, such as with a battery tender, always make sure you connect the negative of the charger to the top of the IBS and never directly to the battery terminal below the IBS.

Ideally, you charge both batteries even when replacing only one, and do an IBS reset at that time.

If N7 or N3 of that high current fuse array are blown, you have issues.
N7 is how the alternator connects to the batteries - if that's blown, they can't charge and it will read only battery voltage which will be low.
11.8 is pretty much a dead battery - or, it means the truck is running off the batteries and pulling the voltage down low.

What do you mean by blown? What’s best method to use voltmeter to check? Red to post, black to main ground?

 

[Lost1wing]

Charge the batteries OUT OF the truck. Charge before installing.
If you ever have to charge the batteries while they are in the truck, such as with a battery tender, always make sure you connect the negative of the charger to the top of the IBS and never directly to the battery terminal below the IBS.

Ideally, you charge both batteries even when replacing only one, and do an IBS reset at that time.

If N7 or N3 of that high current fuse array are blown, you have issues.
N7 is how the alternator connects to the batteries - if that's blown, they can't charge and it will read only battery voltage which will be low.
11.8 is pretty much a dead battery - or, it means the truck is running off the batteries and pulling the voltage down low.

I'm not seeing a good outcome if he is only seeing 11.8vdc. I'd like to see the results of the voltage test of n1 n2 n3 and n7 . Maybe he forgot to plug in the ibs? I wonder what the alternator will put out if still disconnected?

 

[ShadowsPapa]

W

What do you mean by blown? What’s best method to use voltmeter to check? Red to post, black to main ground?

To actually check a fuse (there are several in that array) you need to disconnect it.
If you simply use a volt meter, it's going to show voltage in any case.

Sponsored