Hi Richard, I retro fitted heated seat pads to my Z4 last year using a kit from ebay, will be much the same for the Z3. I posted a thread on how I went about this on here
The addition of heated seats makes the car more usable as the weather gets colder though Ken. Tony.
zroadster.org
The factory wiring should have been already in place on my 2003 model but I went down the after market route which didnt mean me having to obtain a replacement control panel with the heated seat switches. The ebay kit cost £16 per seat and came with wiring, I located the switches just behind the gear stick in the plastic trim. Power was wired back to the fuse box where Ignition live fuse locations were found and connections made to these. When fitting the pads the seats were taken out and stripped down to fit the base and seat back pads, loads of hog rings so I bought new hog rings and a hog ring tool to put the covers back on once the seat pads were installed. Dont do what I did and switch the ignition on to test the switch wiring with the seats out, it will set the airbag light on which will require clearing with a code reader. Mine was a satellite module on the B post that set the code, only a Creator 310+ Reader could find it and clear the code, BMW INPA or BMW Scanner 1.4 on my laptop couldnt find the fault or clear it for some reason.
The new pads work fine, nice and warm quite happy with the outcome.
