I'm installing Garmin, but I'm sure the shunts are very similar. I have opted to install 2 shunts. The battery shunt is located directly inline between the battery and the master relay on the firewall (in fact, I simply cut the WH-769 removing about 2" and putting 2 ring terminals for connecting to the shunt). The 2nd shunt will monitor the alternator output and I located this shunt on the inside of the firewall - I will connect WH-909 to the shunt (rather than the main bus) and run another wire from the shunt to the main bus.