Entire truck "pulsing" with led light bars+amp on. Took vids.

Alright guys, see if you can figure this one out. Gonna be a fairly long post so bare with me while I try to explain this.. And don't jump the gun here because there's more to it than the title implies..

My lights, actually the entire truck, will sometimes "pulse" when running my lights. Usually it's post heavy/ loud use of my stereo and sub-woofer, coming to a stop/low idle speeds. It's kinda rare this happens. 99% of the time it all works fine even after heavy use of stereo. Only on very rare occasions will it do this. I got a dash cam a few months back and this is the first time I've experienced it since. So i was glad to finally capture it. Because it's very odd. It doesn't even pulse to the bass. Turning it down even off it keeps pulsing. It's just a steady pulsing that varies with engine speed being the only thing that affects the speed of the pulsing. Hopefully you can see it good in the videos:

https://youtu.be/Vmfl493M5kE
https://youtu.be/iCOPnx_gElc
^^^Doesn't look like it, but at a stop it IS pulsing, but its very faint. Camera doesn't catch it as good. In person it's much more prominent.






So again, this happens at very low speed usually coming to a stop. At idle in drive, it actually slows and almost stops "pulsing". As soon as I let off the brake and start creeping forward, It pulses much brighter. Not faster, just, brighter, or I should say dimmer. Because it dims, it doesn't get brighter. Turning off/on the lights does nothing. ALL the lights at that point are pulsing. Dash lights/headlights/even the engine kinda pulses along with it. Hard to tell but I can hear and feel the engine pulsing with the lights. Even popped the hood to make sure it wasn't the alt belt slipping and everything seemed to be good. And could also hear better the engine pulsing.

I thought this might be a bad ground or maybe some other ecm or wiring issue, but doesn't seem like any of this would be the cause as it only happens when the truck is running. Restarting the truck eliminates the issue. Even blasting the radio at restart doesn't replicate the pulsing.

I'm thinking something to do with the alternator. I do have a DC Power h.o. alt, and it was inspected recently (albeit for ANY issues, due to the case being replaced, not due to this issue) but unsure how it would affect things. Someone (last time I inquired about it)mentioned the belt might be slipping but not squealing, so i assumed that had to be it. But this time I looked while it was running and pulsing, and it seemed to be doing just fine..

Currently I have two light bars running:
20" 15 amps/180 watts
42" 21.6 amps/260 watts

Not sure on the specs of the amp... 1500w I think. With a single 12" pioneer shallow mount. Not sure on the specs off hand But can look it up.

Alt is rated for 180amps, 120 hot idle amps

The alt should be MORE than sufficient. I wouldn't think my amp would cause this big of an issue.. Maybe I need a second battery?? I'm running an Optima yellow top. Again not very knowledgeable with running a setup like that, but was going to research it as I plan to do this in the future. Kinda need it now, but figured things were ok as long as I didn't overload things with too many lights. Which I do have more lights, just they are disconnected/uninstalled for the time being. When this happened before I had more lights. Now I'm down to just the two and still experiencing this issue. So I don't believe its related to an insufficient supply of power. Only thing I can think of is some kinda feedback with everything tied into one battery and the amplifier trips something and cause pulsing, not correcting itself until the truck is turned off/back on. Does this sound like something that needs to be isolated with a dual battery setup? Or what?

 

Do you have relays on your lights?

Edit: nevermind, you said its every light in your truck...

Its more strange that this is not consistent and can be fixed by restarting the truck... and this only happens when you have your light bars on?

 

Yep. It's like it overloads and trips something, with heavy use of the radio when the light bars are on, to make it pulse. Then it doesn't stop once it's started.

 

Your basis for that thought (reduced load of disconnected stuff) 'seems' logical, but if there is a problem with a component, it won't even operate regular load correctly, much less extra.

I'd bet on a voltage regulator issue, an alternator issue, undersized wiring on the larger accessories, or a combination of all.

I don't know where the voltage regulator is in your truck. Some vehicles have them in the alternator, some have them in the ECU.

I'd find a good local electrical shop (one that rebuilds things right there) and get a load test on the alternator and a confirmation of proper operation of the voltage regulator.

When chasing gremlins, always do the basics first.

 

Hm. Well I'd Probly have to send the alt in to be tested. It has an internal voltage regulator. I suppose itd still be able to be tested like if I take it to AutoZone. But I'm not sure I'd be able to find anywhere reputable or trust worthy or knowledgable about my current setup to tinker with it. I was hoping that I could resolve it myself. Its not a huge deal as it's not debilitating for the truck. But would like to get it fixed nonetheless.

I'm wondering though, if it could be wiring. I did think that a couple of my wiring jobs had a bit too small of wire gauge for my light bars. And planned on redoing it all. It is kind of a rat's nest of wires under the hood. I plan to rip everything out, including my hid wiring, and redo it all professional like with a relay box and loom and just all out.

But again I just find it strange that this issue is isolated to only happening under specific circumstances, but corrects itself in a restart. Can a voltage regulator do that? And will it affect the engine as well like it does?

 

30 miles from you in a quick search. There may be more.

They don't need to know your setup. They just need to prove that the regulator and alternator are functioning properly and capable of outputting the max amount consistently. You can slip it off and take it to them.

Then it's up to you to determine if the load you apply exceeds system capacity.

 

Hm. Thanks for that. It sounds like it would be a good idea to have it tested. But again, I'd feel more comfortable sending it in to the company. I did pay a fortune for it And they've been great before fixing it. Not sure if they actually tested it like they said. Because the case broke and they fixed it for free Even being my bad, and said theyd inspect it for any other issues while they had it. I can throw my original alt in in the meantime. But it just doesn't seem like the alt would be the cause. At least I'd like to believe so being a $500 alt.

Is there Not a chance that this could be due to everything being wired to one battery thus a need for a dual isolated battery setup?

 

I'd bet something like your amplifier is fuse-tapped improperly and straining a circuit. A big full size LED light bar can pull a hefty current load as well. BOTH of these accessories should be run on independently fused/relayed/switched circuits.

 

Oh they are. The only thing that might be of issue with that is maybe the wire gauge for the 42" is too small. Can't remember the wire I used. I wanna say it's 14 maybe 16. Was eventually gonna upgrade it to 12. But I still don't see how it's causing the entire electrical system and even the engine to pulse like it does.

The amp was installed a long time ago. I made sure to use high quality stuff. Can't remember off hand what I used but it's wired up and grounded properly. But it's wired independently. Just like all the lights and other accessories I have. All lights are fused and relayed. Only other thing I can think of, is my led bars are wired into my high beams. The activation circuit is tapped directly to the passenger side h4 socket that is unused from the projector retro. Both low and high beam is tapped since its negatively switched. Specifically the ground and activation circuit on relay tap into low and high beam wires. So when high beams are on, the low beam becomes the ground. Iirc that's how it works. That's the only thing I can think of possibly causing issues. But is that enough to cause what it's doing? I suppose I could try disconnecting the light when it happens again and see if there's any change. Because at this point I'm not ready to start tearing my alt out until I find the time to redo all my wiring. So I'm basically looking for possibilities to eliminate this from happening in the future when I redo all this.

 

It's not wired independently if you tapped the headlights at any stage.

 

it sounds like this could be taken care of with a big three upgrade (couple threads on this) if you haven't already done so, and a capacitor for your sound system. If your lights are all on separate circuits then the common denominator is the alternator/battery setup. This happened to me in both my pickups when I had my Type-R 12's bumpin'. Another option is an aftermarket alternator that puts out waaay more amps than stock, like 200 vs 80-100(not sure what comes stock).

 

Well, they are wired 'separately' I meant to say. With their own relays and fuses and whatnot. I guess I misinterpreted that, heh. But the lights are grounded themselves, and the relay is being grounded through the low/high beam ground. Can this cause issues for sure??

 

I do have a big 3 upgrade aquired from a member here. And my alt is a 180 peak, 130 (120hot) idle amps. Which is Probly more than double what the stock can push out at idle.
And I will look into a capacitor. The amp was installed With the help of a friend. But it's a basic setup. Mono amp with a single 12. I didn't think it would be enough to cause issues. But maybe it is.

Plus I assumed it would just cause the lights to dim to the bass if anything when blasting. Which it does while crusing, but barely noticeable. And that's With it cranked to the max. But did not expect it to cause this weird pulsing issue that's not even affected with changes to stereo load once it's turned down or off.

I've been out multiple times though in the past, creeping along off road, radio blasting, when I had even more lights connected than I do now, without a hiccup.

 

So I just read up on what a capacitor actually does for your system, as I'm not very knowledgeable in amplifier/sub setups, and seems like this may be the source. I'm gonna order one up and install it and see how it goes. Seems like a cheap thing to try for a fix in the meantime anyways. Sounds like I need one regardless.

Is there any way to "test" the system to actually know if it's needed? As well as if it actually helps after the install? Anything I should be further aware of regarding the stereo system and cap install other than the specific instructions of how to install it which I read is a bit precarious(discharging and charging the cap)?

 

Well shit. Really gonna have to look into this. Haven't got a capacitor yet. Been putting this off. But it just happened again today during the day. So no light bars on, radio was turned down. Truck was running a lil rough. Then noticed my dash lights were pulsing again. Turned truck off then back on and it was fine again. So apparently it's not related to the amplifier. Gotta be the alternator or battery. No clue what's triggering it. Voltage seems to be good. Think I'm gonna put in my stock alternator and give dc a call.