What in the world just failed on my truck?

2010 5.7 CM,

Issue started with my turn signals going hyper flash (resistors are installed) at random. Sometimes they're normal and then Hyper Flash. Others, they HF and then go back to normal.

I Suspected bad resistors... until:

Just now, driving home, ABS light, Brake Light, and Traction light come on solid. Then volts drop to Zero. Shortly time later stereo starts flashing but music keeps playing, then speed goes to Zero (but bounces at random from zero to current speed and back to zero).

Temps are all good. Fuel and rpm gauges are working.

I managed to get her home, but starting from a stop became rough as time went on.
Once home, I turned her off and gave it 10s and now it won't turn on.

I'm wondering if the high output alternator I installed 2 months ago died?
Any ideas? This feels like the ECU is going out, but I'm paranoid atm.

 

Is your battery okay? Have you load tested it? Trivial questions but these new trucks go crazy when the batteries go bad.

 

Even on a 2010?

 

I would say so. I had a battery ground connection go bad due to corrosion on my 08 Silverado. Absolute poltergeist action. Locks locking/unlocking, dash losng partial power, gauges going wild, lights flashing, engine partial stalling, then quiet for days on end.

 

I'm running 2x batteries and I agree I need to test them. It's been one thing after another with her lately. ugh...

 

Definitely sounds like alternator to me. Not sure why it would go out prematurely though.

 

Exact same thing happened to me in a Yukon XL. Dash lit up, locks fluttering rapidly…we thought it was possessed. Turns out it was a bad connection to the battery.

 

Ditto...replace those cheap stock batt connections.

 

Sounds like mice. Check to make sure one hasn't been eating some of your wires.

 

Pulled the batteries. Primary was at 11.2vdc. The secondary was at 9.95vdc. Terminals def. Need to be replaced.

Because the 1 battery is so low, I'm leaning towards the alternator. But there is a chance my battery selector could limit the alternator's ability to charge it?

Additional:
- I checked all of the wires (all were already upgraded, 1awg from alternator and 4awg for all grounding points) and all were tight, w/o movement.

- I'm going to install dedicated volt meters for each battery. I figure if there is a charging problem that will show it rather fast.

- Finally, I checked and didn't see any evidence of mice or even worn wires. -- Though I admit a deeper review might be needed.

 

Both batteries have now been replaced, and thankfully they were under warranty.

I took a new battery and set it up in the engine bay and made sure my bat. selector was set for that battery, only. The truck turned on without hesitation.

Then, let her run for a bit and then yanked the positive terminal off the battery. The truck continued to run, but I noticed the front running lights were slightly flickering.

Checking in the cab, the built-in volt meter was bouncing around. -- Not good.

I gave a small tap of the gas, and she instantly died.

So, yeah... AFAIK that can only be the alternator If I'm not mistaken?

 

What’s the voltage at the battery with the engine running? These modern vehicles aren’t designed to run without a battery like older vehicles…

 

Voltage will fluctuate like crazy without a good battery installed. That can damage things too, so be careful. I’d lean toward the alternator from what you describe, especially if your batteries test good otherwise.

 

1. Hello fellow AZ owner.
2. Plz forgive the picture #1, I haven't cleaned up the wires yet, let alone installed the new terminals.

3. With the battery connected, I have 13.81 - 13.86vdc. There isn't any flickering with minimal load.

W/ low beam and fogs, this drops to 13.76vdc.

W/ all extra lights on it drops to 13.67vdc.

 

I’d say your alternator is working as designed. I’d normally see 13.1-13.5v before adding a HKB voltage booster.

Good taste in DMM. Where ya at in AZ?

 

Thank you! It's a relief to hear that about the Alternator and DMM.
I'm just north of PHX, in the Desert Hills/Anthem area.
You?

Side question for all;
I'm debating if a battery selector is the right way to go?

Even with bat 1+2 selected, I'm not convinced bat #2 is being charged correctly. So, I'm debating deleting the selector in favor of an isolator, which should balance load and ensure both batteries stay topped off?

I'm also debating modifying the grounds which currently go to the chassis, and adding a 4awg run that goes direct from the neg terminal on bat #1, to the neg terminal on bat #2.

Thoughts?

 

I’m in Oro Valley about 20 minutes NW of Tucson but meet-up with the basin crowd every few months to run a trail.

Is it possible your second battery had a bad cell? A Blue Sea ACR seems to be the preferred choice for this type of setup.

 

That’s how mine is set up. 3 years and no issues. Here’s a link: https://www.tundras.com/threads/quick-easy-cheap-and-versatile-dual-battery-setup.92655/

 

Great thread! Appreciate you sending this over.

Our setups are nearly identical, with the exception that I thought I could get away with a selector switch only, and should have used an ACR. That'll be the next Amazon order.

Until then, I'll use the selector to keep the primary battery operating.
Really appreciate all of the help and guidance.

 

Alright...

I replaced and redid all of the wiring to the primary battery, as shown in the image. Test run started great, but failed.

- 4 mile total test. 2 miles to get gast and 2 miles home.
- Initial 2 miles were great. Zero issues.
- Return trip started with the built-in volt meter showing half way between 9vdc and center (12vdc?).
- By the time I got home the truck was starting to act up, gages starting to jump around, etc.

I threw my DMM back on, and the new battery was showing 11.95vdc and falling, slowly.

Any ideas? I'm still leaning towards the alternator.

 

Agree. You should be always getting at least 13 volts with the engine running if the alternator is working properly. Sounds like a bad regulator since it’s sporadic.

 

Well, the replacement alternator has been installed, but I have concerns.

The brand new unit whines, initially at idle and increasing with RPMs, but settled out w/o the whine at idle and it only came back under load.

A voltage checked showed that, at idle, I was getting 12.56 - 12.67vdc.
Under load, it never went lower than 12.3vdc.

I hate the idea that this unit has issues. I really don't want to be installing another alternator in 115F heat.

 

Did you use a Denso? That voltage sounds low.

 

No, I actually bought a high output from Tucson Alternator.

 

Ruh roh. I’d send them an email or give them a call Monday. They rebuilt my original for me for a reasonable amount but it just needed bearings…

 

Agreed. Let's see if I can install a 3rd alternator, but in less than 1.5 hrs.

Ugh, I'm feeling cursed.

 

Did they send out a test slip with the new one? This is what they gave me with my rebuild -

 

Yes, Sir - They sure did.

 

Weird mine has voltages in the feedback rows and yours doesn’t.

You definitely aren’t seeing the 14.5 it’s set to. Is your alt-s fuse unmodified?

 

100% sounds like your alternator. Mine gave way on my old fordwhen I was in stuck in traffic just outside NYC. These trucks are designed so that the ECU and ignition circuit are the very last to operate. Truck was bucking like a bronco with dash was completely black. Luckily made it to orielly’s but that alt failed in 4 days. Got a replacement and that one crapped out two weeks later. Finally got my money back and paid for an OEM and it last 70k until I sold the truck.

and just because the alt gives correct voltage/amps when at idle doesn’t mean it acts the same under load.