14. After mounting the relay switch, run the necessary wires through the firewall and into the cockpit. Mount the on/off switch(es) in a convenient location near the driver. Being that we're not smokers, we mounted our switches on the bottom of our ashtray. When the need for nitrous arrives, simply flip the switch and you're ready for action. The switch on the left is for our bottle heater (optional) and the other is our on/off switch.