There is a harness for the heated seat / heated grips it dose both you will need to buy !!! The harness plugs in to the left side panel / shifter side panel and you can add the seat and grips. Harley stopped putting a plug in under the seat some time ago. if I remember its around $35.00 bucks. Sorry I just don't have or know the part #.
Dante
The limited cvo models have the harness already installed for the heated seat. The accessory harness for the m8’s (not sure if it’s different from earlier models) has multiple plugs, the one for the heated seat is switched on with ignition on once the harness is plugged into the accessory plug next to the abs module under the right side cover. I believe on the earlier bikes it used to be under the left side cover. There is additional wiring on the harness to wire directly to the battery for the other plugs but for the heated seat connector, you just need to plug in the harness. On my 2022 rgl, I simply tied off all the other wires since I only needed the heated seat connection.