Check the voltage at the light bar with the light bar on and compare that to the voltage at the battery terminals. You should not see any measurable difference with proper wiring. I'd suggest putting a relay in and wire the bar directly to the battery. Power the relay coil with the power from the Aux. switch. This way there is one relay contact between the bar and the battery.
I had thought about using Aux 1 to trigger the relay on the harness that came with the light bar (since the noise level was reduced) but never got around to testing that. I thought that was the whole point of the Aux switches, and figured that might be putting a band-aid on the situation long term. Plus, I boxed the light up today since the manufacturer actually replied back and acknowledged the light should not display these symptoms regardless and offered a refund. However, for the sake of knowledge, here's what I did test:
Vehicle running, no light bar connected:
Aux 1 > Ground point: 14.00V
Aux 1 > Negative Battery: 13.98V
Negative Battery > Positive Battery: 14.01V
Vehicle running, light bar connected to Aux 1 (measurements at same spots):
Aux 1 > Ground point: 13.07V
Aux 1 > Negative Battery: 13.08V
Negative Battery > Positive Battery: 14.01V
Vehicle running, light bar connected direct to battery
Negative Battery > Positive Battery: 13.97V
Vehicle running, light bar powered by provide harness
Light bar positive (at wire harness) > Negative Battery: 13.58V
Negative Battery > Positive Battery: 14.02V
Obviously, as pointed out, there is a decent voltage leak somewhere. My guess is something grounded in the light the battery was able to compensate for that the Aux relay wasn't? Or the waterproof connecter, since I never bypassed that. It's been a few years since my EE classes ... plus, when I did this last night my productivity level wasn't super high
If I missed an obvious test, let me know ... I'm picking up an even cheaper light bar tomorrow just so I can have something at TRR and still want to ensure the vehicle's in order.
