ChrisSchinell

I just installed a new car battery in my 2009 RX350 and since then the passenger side heated seat comes on by itself at the highest temperature even with the switch set to the off position. I removed the switch from the dash but the seat still heated up. I was finally able to disconnect the seats power connector under the seat and it no longer heats the seat but I also have no adjustment power to the seat. Also pulled the seat heater fuse and now I want to check the relay for the heated seats but don't know where the relay is located. I'd appreciate it if someone could let me know their thoughts and the location of the relay.

MattRX

I would pull out the seat and check on the heated seat module. There's a chance it could be blown up. Something similar happened to the previous owner of my car's seat before it exploded and melted. I replaced the module and all is well. The symptoms he reported were identical to yours.

https://www.clublexus.com/forums/rx-...eat-fried.html

ChrisSchinell

Thanks for the suggestion. I'll see if I can detach the seat and get under to check the module. We did notice an odor like burning plastic so that might be it. The seat continued to heat up but I guess the module (is it considered a "relay"?) regulates the amount of heat to the seat. Not sure when I'll get to it but hope it's soon and I'll post an update when done. Wonder if something happened when I replaced the battery as it coincided with that and strange thing was that other things like the back hatch door button didn't work and the drivers side controls for passenger side and back windows wouldn't work either. I used the remote to lift the hatch and that reset it and I used each doors window buttons to reset them. Once they were used then the drivers controls worked again! Something needed resetting in the electronics but since then the passenger seat heater was messed up and heated till we could smell that it was heating up too much. Just adding this stuff in case anyone is interested and has had a similar experience when changing the battery.

ChrisSchinell

I just saw a video on the Toyota forum that shows the relay box in the engine compartment and mentions that the Lexus RX350 relays box is under the brake fluid cylinder so that's another thing to remove and check out. Fun fun fun on the Autobahn!

MattRX

I removed the master cylinder on my car and there is no relay box there. There is however, one in the interior on the driver’s side down where the steering column is