Hi

I had this problem on my 405 Executive & now ive solved it.

The cause is that Peugeot FORGOT at the design stage to install a
thermostat in the seat heater, So they just burn themselves out.
Even Peugeot technicians laugh at this fault.

New elements are very expensive, You would be talking around £150 per seat
just for the parts, They can be repaired if you have skill with a soldering
iron.

Basicly its 2 x heating pads, One on the base & that joins upto one in the
back rest, They are wired in series.
Both have to be working to get heat out of the seat, Normally the base pad
fails at one of the joins between the gaps in the cushion, The back rest
hardly ever goes wrong.

This fix needs the seat removing from the car & stripping down, The frame
has to come off the base & the leather has to come off the frame.

Its a very very involved task to do, It took me about 4 hours per seat.

A £5 thermostat kit from Maplins works wonders, My heaters now cut out at
30 degrees & no longer burn themselves out.

If you want more info on this then just ask.