Electrical problem. Please help

So it all started one day when driving my truck shut down our of no where. It would happen when I turn my lights on or turn my stereo loud. It had been working this way for years so I figured my alternator gave up. So I replaced my alternator with the Suzuki 105amp denso, I replaced the alternator to fuse box and fuse box to the batter as well as the ground cable with 4awg cable. I finally replaced the battery with a new AGM battery.


With the upgrades you would think I can run all kinds of lights and a winch but as it sits it seems like my electrical is just enough to keep it running. Sometimes when I turn on my signal light it shuts down. It’s so bad that my electric fan won’t turn on when hot.


If anyone knows anything that I can look at I would appreciate it. Thanks. Here is a picture of my truck for attention.

 

There are 3 basic components to the system. Correct troubleshooting is to test to determine which is the basic culprit.

The 3 systems are the (1) battery, (2) alternator and (3) the wiring that connects those two components to the truck and each other.

Do you own or have access to a multimeter? You need something to measure voltage and also continuity.

 

Yes I have a fluke. Just to note I am an electronics technician so I understand electrical jargon.

 

Then you've likely tried some of these things in your troubleshooting.

What is the resting voltage at the battery?. Check this when the truck has been off for a while.

Likewise, what is the voltage at the battery when the truck is idling?

 

Off is 13ish VDC and running 14.1VDC. I went and ran the truck I noticed when voltage is being pulled down my signal lights go hyper flash. So I started pulling fuses and nothing “fixed” it. I have two circuit breakers. One for my stereo and another for my air suspension. Neither “fixed” it.

but I did notice that the fuse box under the hood was about 12.5VDC and under the dash was 11.7vdc. I didn’t know that there is that much of a voltage drop.

 

Do you have a capacitor in your system to store voltage for your amps?

 

Yes and when I remove it (tripping the stereo breaker) It still the same. I was gonna take it out by removing the cable because at this point I’m gonna remove my amps and sub. And just have front and rear speakers running off my headunit if that means I can drive my truck again. Lol

 

Check voltage coming out of back of alternator bat post compared to battery terminal. Check your body grounds really good. Check resistance from neg battery post to body with truck running.

 

There should not be a voltage drop.

On my Truck I have system Voltage read the same every place from the tail lights to the engine bay.

I would look for physical damage or corrosion in the harness.

 

From the OP description it sounds like the system Voltage to the ECM is dropping below the thresh hold voltage.

Causing the ECM to go into self protection mode and shut down.

Just how is your sound system connected a switched power relay allowing full system voltage to the sound system and not drawing off any other circuit??

Why would you use such a small gauge cable for the ground?

 

Sound system is through a 100a circuit breaker. But I open the circuit so it’s on connected. And I didn’t know 4awg is a small ground. I guess I can buy some 0/1 gauge cable but I don’t think it’s necessary

 

4AWG is plenty. Good Lord, you're running a stereo not a 10kW 3 phase generator.

 

someone did bring up that I didn't strip the paint where I added a new ground so I'll do that and add a ground from my engine block to the frame (with 4awg cable also)

 

Hey guys so I decided to address the battery ground cable. I never sanded the spot where I put the ground. I cleaned it off and put the battery cable and and voltage everywhere was back to normal.

 

Glad you found the problem.