I tapped my 8500ix directly to a wire coming from the BCM/Fuse Panel. If you take the storage cubby out and look at the panel, you can see a loom of wire going up from the panel (attached to the panel by a large connector). Moving or removing some of the tape you'll find a brown wire with a yellow stripe. This wire is attached to fuse 23 (10A). This circuit is used to enable/power on the DC/AC Inverter, Vista Roof Module, and Driver Door Controls so they don't use very much current. It's a pain to get in there and find the wire but once you have the wire isolated it's pretty easy. Just be sure when you tap to it to put an inline fuse close to the tap to keep the wiring safe (I used a 3A fuse).
The other option is to use a Micro Fuse Tap (Type ATR) and tap into Fuse 23. This is the safer option but was a bit of a hassle for me because no auto parts stores near me carried one in stock.
I chose Fuse 23 because it's attached to accessory power. The radar does not turn on until I start the engine and shuts off after I turn off the engine and open a door.
Technical details: From BCM, using Accessory Delay Relay, Fuse #23 10A, Connector C2280F Pin 30, Circuit CBP23, Color BN-YE, 22 Gauge Wire
I tapped my 8500ix directly to a wire coming from the BCM/Fuse Panel. If you take the storage cubby out and look at the panel, you can see a loom of wire going up from the panel (attached to the panel by a large connector). Moving or removing some of the tape you'll find a brown wire with a yellow stripe. This wire is attached to fuse 23 (10A). This circuit is used to enable/power on the DC/AC Inverter, Vista Roof Module, and Driver Door Controls so they don't use very much current. It's a pain to get in there and find the wire but once you have the wire isolated it's pretty easy. Just be sure when you tap to it to put an inline fuse close to the tap to keep the wiring safe (I used a 3A fuse). The other option is to use a Micro Fuse Tap (Type ATR) and tap into Fuse 23. This is the safer option but was a bit of a hassle for me because no auto parts stores near me carried one in stock. I chose Fuse 23 because it's attached to accessory power. The radar does not turn on until I start the engine and shuts off after I turn off the engine and open a door. Technical details: From BCM, using Accessory Delay Relay, Fuse #23 10A, Connector C2280F Pin 30, Circuit CBP23, Color BN-YE, 22 Gauge Wire