Humming noise after starting truck

Hi All,

First post on this forum/website and its a bit long winded.

I have an 06' Toyota tundra that I have been having trouble diagnosing an issue with.

About 2 weeks ago (09/04/2021). I started my truck an noticed a humming noise. The humming noise has only occurred 2 times that I have heard. Once when I first noticed it and once today (09/21/2021)

When I first experienced this issue, I checked my instrument cluster and noticed the battery gauge was ticking around 12 volts. I usually see a 14 volt level when idle or driving the vehicle around town.

Immediately took my vehicle to AutoZone to have battery inspected as that is where I purchased it in 2018.

Was told my battery had a 74% charge. All the other test had must have passed because they did not mention anything other than the charge level. Employee that checked the battery recommended I leave the battery and charge it, so I did.

I came back and reinstalled the 100% charged battery and had the employee rerun the test with their diagnosis system. It had shown the battery at 100% charged, obviously, but this time had shown my alternator had failed the test. They recommend I get a new alternator.

On 09/06/2021 I took my truck else where to get another opinion.

Took my vehicle to Jiffy lube for an opinion because they were responsible for changing my serpentine belt in 2020, and also happen to change alternators. Just like AutoZone they ran their diagnosis and had shown a okay battery but with no failing alternator this time. They reviewed the serpentine belt and there was normal wear but did not need to be replaced just yet.

They recommend I start the car while they remove the negative terminal. They suggested it was the "old school" way to check the alternator. Once done, it had passed that test in their eyes. The only thing they could think of was that the issue was with the battery.

I took my vehicle to another AutoZone after visiting Jiffy Lube and had them rerun a diagnosis. Battery came back 100% charged and had PASSED the alternator test.

At this point I was confused as I was receiving conflicting info and told them this based on my experience I had already gone through. There was nothing that this AutoZone could do evidently because if the battery has passed their test they could not replace it unless it read BAD. I decided to drive my truck home an look for other options.

On 09/15/2021 I took the truck for a drive and everything seemed to be operating normal. I drove my vehicle back home, parked it and attempted to lock my doors before I noticed my vehicle started to act up while attempting to do so. I removed my key and attempted to restart my vehicle but had not luck. When I put my key in the ignition "start" position they dash lights came on but were fluttering. I tried to to turn on the vehicle and got no crank.

I decided to remove my battery after attempting to start my vehicle 4 more times with out any luck. I removed my battery because it was just charged at 100% and if the alternator was truly bad I did not want to drain the battery.

Once this happened I had to wait a few days for a family friend to bring a battery jumper. When the family friend came by with a battery jumper I reinstalled the battery in the vehicle for them to get a reading on the battery. Per the reading the battery was putting out 12. 65 volts or so without the vehicle on, which is about right on a battery I believe. Once done we tested the battery with an attempt to start the vehicle, and alas the vehicle started without having to jump it....Ironic really. We tested the battery with the vehicle on and the battery did not seem to be the issue and had the right readings.

On 09/19/2021 I decided to go to another AutoZone and I requested my battery be replaced as it was in the final months of warranty. They honored that change and replaced it. This was to remove any thought that it could be an issue to the battery.

This brings me to todays date where I have heard the humming noise again after starting my vehicle. Not sure what the issue is and looking for some hep leading to a possible diagnosis and solution.

I have attached a picture for reference.

Thanks for any reasonable help.

 

So many questions for a 183k mile truck, but I'll ask these two:

Has the alternator ever been replaced, either since the truck was built, since you owned it, or since this started?

Do you own a digital multimeter or voltmeter and know how to test an alternator, both at its direct leads, and at the battery terminals?

 

Sounds like a bearing on the drive going bad causing the humming. Alternator is definitely suspect with those numbers.

 

Can the humming be the secondary air injection pump being stuck?

 

Battery cables. Check 'em for corrosion and good connections. Big 3 upgrade is good too. Without ground, there is no powah!

 

Alternator has never been replaced before and unfortunately I do not own a multimeter or voltmeter.

 

I read this was a possibility some where on another forum and have a video I took of what my vehicle sounds like but Website wont let me upload it due to the video extension.

 

What is the big 3 upgrade?

 

If alternator never replaced, I would be highly suspect. Mine died at 15 years old and almost burned down my truck, and I only had around 60k miles at the time. 183k miles on the original alternator is a good run. Consider replacing serpentine and any applicable tensioners at same time, and go OEM Denso on the replacement alternator.

I'd recommend to invest in a cheap digital multimeter (DMM), they're really not that expensive. If you were local, I'd straight-up give you one of my extras, I've collected a few throughout my life for some reason.

Once you have a DMM, you can easily test battery, cables, alternator to see what's going on. I agree with @THinTX that low hum would suggest bearing. If it was SAIS, I'd expect more of a high pitch whine or squeal.

And as much as I really don't like this guy, this video does give you everything you need to know about battery and alternator testing, maintenance, etc. once you get a DMM.

https://www.youtube.com/watch?v=YC--MLNIbik

 

Factory grounding cables in the engine bay were on the small side. Grounds allow the energy used by the vehicle to flow freely through the electronics. It has to have somewhere to go. The Big 3 upgrade replaces the small gauge grounding cables found under the hood with larger gauge grounds to "improve" grounding efficiency. Helps clean up erratic electronics behavior and "noise" in the electronics. There are several threads on this forum that describe where the cables are located and how to swap them. Many have high mileage rigs with no problems and have never done the upgrade. It ain't a problem unless it's a problem. If you got problems, might be worth the upgrade.

 

There are indeed….thanks for that

https://www.google.com/search?q=big....com&ie=UTF-8&oe=UTF-8&hl=en-us&client=safari