Sometimes that works, sometimes it doesn't. Sometimes if you do that, you get backfeeding through the turn signal switch, and everything lights up at the same time.
Whenever we wire up vehicles to tow behind motorhomes, we always run dedicated wiring along with diodes, to prevent any feedback. This separates the two systems.
Casey
1995 K1500 Tahoe 2 door, 6.5LTD, 4L80E, NP241, 3.42's, 285/75R16 BFG K02's; 1997 506 block; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, HX35 turbo, Turbo Master, 3.5" Kennedy exhaust, F code intake; dual t/stats, HO water pump, Champion radiator; Racor fuel filter