In looking at the parts diagrams they appear to use the same main wiring harness from about 05-09 except on the RTPs..(thatís a whole Ďnother story).
If he wants to stay with OEM stuff the heated seat switch is inboard of the grip switch and usually includes the trip computer (BC) switch.
I did not see a retrofit switch assembly that just has the seat switch...looks like the whole switch assembly has to be replaced.
Of course on the 2-piece BMW seats the rear seat has itís own switch incorporated into the side of the seat. I have the 1-piece BMW heated comfort seat and it has a rear heat switch on the side as well...both the front and rear seat switches talk to the bike computer to set high/low heat levels.
The controller on the bike sets seat heat by sending voltage pulses to the seats at one cycle per second...on high heat it sends 14.1V; on low the pulses are 8.5V. The typical resistance of the front seat heating element is 9.5 ohms...
These heating pulses come out of the central electronics unit (ZFE) on pins 16 and 8 respectively for the front and rear seats.
It may be easier to just add a relay, fuse and a separate switch somewhere and feed it off the battery depending on your skillset and how much $ and time you want to put into this project, but with the factory setup you get two
levels of seat heat thru the controller on the bike, not one. If you do the switch/relay/fuse solution youíll only get high heat.
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