On our 28RKX Wildcat Maxx that toggle switch is for the tank heaters to keep the tanks from freezing in cooler weather!
As far as the popping goes, are you sure it's not the WD hitch ( assuming your using one)?
Does it happen only when you apply the brakes? Could be the brakes "grabbing" due to being brand new!
Days camping (2016)----181 days
Days camping (2017) --- 82 days
2016 Wildcat MAXX 28RKX (33' TT), 2007 13' Scamp
2015 Ram Laramie Hemi, w/air suspension
30 years RV'ing
11 different RV's