RX400H Heated Seat Switch Issue

[Webhotchilli]

Hi all

I have a 2007 RX400H which has been pretty good all in all. Had a new inverter and hybrid Battery which hurt, otherwise not bad though. 

Recently my passenger side front heated seat light stays on, even with the car turned off and locked. I am not sure if the seat heats whilst the car is locked, but it seems to be on low when the car is running. 

I know the relatively small front batteries can drain on these cars and I am having to use a Battery pack to help me start on every drive as the Battery is drained, even after being charged. Battery voltage at idle is 13.95v, and switched off is 12.76v, so am thinking the alternator is charging.  

I replaced the switch with a used switch... light went out a couple of days, Battery was recharged and seemed momentarily better, but now the heated seat switch light is on again and Battery is going flat. 

i am thinking to put in a new Battery probably, the old being a 6 year old bosch... but am unsure what is best for sorting the heated seat switch... fuse out perhaps... though I am not sure which one as have seem a few mentioned? Replaced relay perhaps... if so, any part numbers and location?  Or something else? 

Many thanks all