2019 Honda Accord, Rear Defroster Trigger

Does anyone know which wire to trigger to turn on the rear defroster?   I installed a Viper 4816V into my 19 accord because the oem one sucks and the FLCAN doesn’t turn on the rear defroster.

I'm thinking the relay is in the engine fuse box. If you can locate it, see which coil terminal has constant power. The remaining coil terminal should be the control terminal. Use a test light and a piece of wire wrapped around the suspected relay terminal to jump to ground and verify you have the right terminal. You can test for voltage across the rear defroster to verify output.

If you can't locate which wire on the back of the fuse box corresponds, you can solder a wire directly to that terminal on the relay and run inside the cabin.

Alternatively, you can wire your own relay in to power the rear defroster directly.

To go directly from the Viper to the Accords' Rear Defroster locate the wire shown below. It should be thick, ~12 gauge.

Rear Defrost    BLUE (+ ) LATCHED) (+)    DRIVER KICK, HARNESS TO REAR

Set the Vipers Blue/White wire to "Latched Defrost"* output and use this to control
a 30/40 Amp Relay as Lee suggested. Relay wiring below :
Relay Pin 85 to Viper Blue/White Defroster output
Relay Pins 86 and 87 to +12V constant fused at 25 Amps
Relay Pin 30 to vehicle Blue Defrost wire
Relay Pin 87a not used - insulate

* Menu 3, Feature 11, Option 2

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Soldering is fun!