2017 Yukon - Blinking headlights, but alternator and 2 batteries working fine

Greetings, I’ve done a complete audio system change, all speakers are RF power series and added, (2) 400 watt amps and (1) 750 watt amp. I added a second battery to the available spot under the hood. And replaced the head unit with a Sony, and added 26 speakers if you count the tweeters inside all the speakers. After 2 weeks, my headlights started to blink but only at 35 volume, the Sony goes up to 50. When the headlights blink, the volt indicator is still on a solid 14 volts, it will come down a little to 12 volts but only after a long trip and play above 35 volume setting for 60 minutes.

I’ve gone twice to different shops to test the alternator and both batteries and they show they are working good. In the day, when no headlights are on, no power fading from interior lights.

I suggested to the audio shop we add a 3rd battery or I may need a competition alternator, I’ve seen 400-500 amp ones online, seems like the standard Yukon ones are around 150-170. One shop, suggests a battery bank hooked to the amps.

Any thoughts, thanks

The flickering lights are usually signs of a weak battery. Your amperage load when playing music is probably drawing the batteries down and the alternator takes more time than normal to recharge them. I would look into those Mechman I think they're called alternators. Lots of guys on here have them and know more than I about them.

Remember, batteries ought to be replaced in pairs. The older/weaker battery always draws down the stronger one.

@Doubeleive

sounds like the alternator is under rated for your system, probably need to double the output
a fresh set of battery's wouldn't hurt either.
this is just what happens when you up the voltage draw on a vehicle, be it audio, lighting, ham, tv's, whatever.
and the bottom line is it just takes money.

1500 total watts is not all that much, particularly when you are having issues with the volume at only 70% of maximum. Did you use #2 or #0 gauge heavy cable for the power feed directly from the battery to the amplifiers and the same heavy gauge cable for the amplifier grounds to the chassis? Too light a gauge power wire will restrict the instantaneous amperage pulses when the amplifiers draw power (like for bass sounds). Many folks also change out the cable from the alternator to the battery with the same heavy gauge power wire. This is known as the Big 3 Wiring Upgrade. If you don't have this heavy gauge cable already installed, please upgrade and get back to us with the results.

Thanks for all the detailed info, I will check on the cable gauge with the installer.

Halas Empire said:

Thanks for all the detailed info, I will check on the cable gauge with the installer.

Click to expand...

"After 2 weeks, my headlights started to blink but only at 35 volume"
this tells me weak battery and poor charging system, been down this road before..........

The car installer used #0 gauge wiring for everything. I was there today and when we turned in the headlights and fog lights and went to 100% volume, the headlights and fog lights wouldn’t blink at all, made me look like a lunatic. I did just drive 20 miles to the shop. All my blinking is from going to work and driving 1/2 mile.

I added a second battery, duralast 800 cca battey when I had the initial install done. The installer talked me out of replacing the 1st battery which keeps getting a good charge, but it’s a everstart 800 cca Walmart battery, I went through a a lot of bad everstart batteries back when I didn’t have a system. I will get anothe duralast battery tomorrow.

The installler thinks the headlights need to be replaced with led bulbs. Past a better battery and led headlights, it could be a bad wire in the bunch that was used. A alternator replacement could fix it all, at 140k, I will be replacing it soon, definitely will get a Mechman brand 400 amp.

I ended up ordering a mechman 370 amp, it caught my eye that it was recently redesigned in 2020. It keeps the alternator at 200 amps when idling. Replacing the headlights with led might help a little, but I want a lot of help so I can run the ac, wipers, with the radio. And I would like to eventually add on more 15 and another 750 watt amp.

I didn't want captain chairs for the backseat, but here is a unique box Wizard Audio from Oxford, AL made for me.

On batteries, I didn't get another Duralast, online searching found out Duralast and Everstart are the same manufacturer. If I replace both batteries at the same time, Diehard Platinum seems to get a lot of good reviews.

Do you have capacitors installed near the amps? They will stop the voltage surge at the battery. The recharge in micro seconds and are not like a battery. If not add a 5 to 10 Farad capacitor. You can go bigger, it won't hurt.
When they added cables for the amps and battery did they take the time to remove the paint and primer where the grounds connect? I've seen people just use seat bolts. The grounds from the headlights need to be checked too. If they ground to a fender, clean the mounting to the fender and then check the fenders grounding to the battery. OR run a new 10ga wire to the battery negative post, just for headlight grounding.
If the new battery is connected to the fender and the headlights are grounded to the same fender BUT the fender is grounded to the battery with a 12 ga or 10 ga wire it's not enough for the amps.
I doubt your 3 amps are drawing over 120 amps average so the factory alternator should be okay until you add more amps. Make sure everything you add has a clean and tight connection to the ground system (frame) It's not needed to run a separate wire to the battery negative post. I have run a 0ga or 00ga to the amps and added a buss bar in the rear to make the ground connections. It's like a fuse box for grounds but without fuses. There's no need to fuse both sides in this case.
When you added the second battery, what size cable did you use and how did you connect them to the original battery? This is where the batteries with side mount AND top posts come in handy. I have used the side post with 3/8" lugs. Put a nut on a 1" long 3/8" bolt then put the 2 cable lugs on the bolt and install the bolt into the battery. Hold the bolt head and tighten the nut down to tighten the lugs.
When you get this resolved please come back and let us know what it was. People will see this post for years and we may be helping many people. Help stamp out dead end threads! Good luck.
I've only been doing this stuff since 1977, so if I have something wrong or outdated I apologize. I hope to get out there tomorrow and learn something new again.
Note about alternator size. I had a 4 channel 960 watt amp, the head unit, a VHF radio, a 1,000 watt
color fishfinder, a 6KW radar, tons of lights, live well pumps and a ton of other stuff on a boat with 2 batteries and 2 outboard engines, each engine had a 50 amp alternator. I never had a battery load problem.
Good luck,
Willy

Thanks for so much details. I will add some pics of the batteries and the fuse thingy the installer added on the installation to the main battery, asap. He hasn't added any capacitors yet. Looks like 2-3 weeks in the new alternator, headlights replaced next Friday, but I will keep giving updates, thanks for replies.

The 370a alternator probably overkill for my issues, but at my mileage, mine won't last much longer and by getting it now, I can get the custom one instead of whatever is available whenever it goes out.

One other thing that could be causing my headlights blinking, I replaced the head unit and can no longer use the "Electical Power Management" app. I got the Sony ES 9500 and it retains a bunch of the original apps, but can't see the EPM any more.