My experience is that removal of the red wire depends on the speedo. I had a Novak 410 years ago and it required the red wire from the speedo to the receiver be removed. When doing that, you must turn on both switches. But the LRP Quantum can be done both ways. Just remember that you must turn on both switches if you pull the red wire. I ran the GM V-12 with an external battery and only used the switch on the pack to control the system, leaving the red wire connected to the receiver. I suggest you check with the speedo manufacturer to find out their recommended practice. Oh, Tekin speedos will work with the red wire in place and you only use the battery switch.