Auxiliary Lighting Causing Weird Bump or Misfire?

[ChibbMD]

Recently installed a 17in light bar and a pair of A Pillar lights. All LED. Light bar on one wiring harness and switch, A pillar on a separate harness and switch. Tonight was the first night since I completed the install and I was testing them out a bit, trying to get everything aimed where I wanted. In the situations where I turned on both the lightbar AND the A pillar lights I noticed the Jeep making a strange bump sound/feeling. I could feel it through the pedals and seat. It wasn't super loud and wasn't harsh or clunky, but definitely noticeable, and definitely there every time I used both lights. It doesn't happen when only one set of lights is on. Seemed to be a small drop in RPM when the bump occurs, kind of like a misfire. No movement in any of the other gauges including the battery voltage.

Seems obvious that it's linked to the draw of the lights, but the resulting symptom doesn't seem like an electrical symptom (i.e. no dimming of other lights). Any ideas what might be going on? Maybe not a big deal, but it doesn't sound or feel right. I wouldn't think some LED lights were really putting that much of a strain on the Jeep.

 

[Gilaguy23]

I wouldent think its a problem either but you should add up the claimed watt ratings of your new lighting and divide the total by 12 which is volts. for example,1000 watts of lighting divided by 12 volts is 83 amps. Make sure you using the actual watt draw or better yet amp draw if its provided on the light boxes. LED typically will say XX watts of power but only uses X watts of power. You could also use a DVM on the battery to see what voltage at idle its seeing. Your charging system may be weak and failing. A drop in idle speed indicates the alt is being worked a bit which is normal but is it no capable of handling the load.

 

[T-Rex Jeepster]

What is the source of power to the lights? If you tapped in Willy-Nilly, You could be freaking out a circuit that the ECM draws info from...ie. Fuel injection. These are circuits that are rated to a certain draw amperage and any upset will have the ECM thinking something is askew and will deviate what it puts out to maintain proper and balanced performance....
Anything added, Stereos, Lighting, Anything.....I always go straight to the battery for power with an independent ground, Fuseable link and it's own switch........

 

[ChibbMD]

T-Rex - I've been thinking the same thing. The A-pillar lights are run directly off the battery with a stand-alone harness from the lighting company, so it's in good shape. The light bar was originally tied into the high beam circuit, but I changed that recently and just stuck it into the fuse block on a circuit that had constant power (I think the clock, lol). I probably need to move that back to drawing power directly from the battery so it's not tied into anything.