Had responding heater switches, coming up red lights when pushed, heard relais clicking but no heat or just a “little hint” when car was cold outside.
Culprit was the thermoswitches in the seat cushions on driver and pax side. These switches
cut out the heat at a certain temperature and it seems with age they tend to do so at lower temps than designed for. Meaning the seat is not warm and they cut already. (You can check them when out with a “resistence-beeper”, cooling them in the fridge and warming them again.
A little “klick” can be heard when it switches open again).
I bridged/shortwired them both and heat is now working properly. The seatheater system has a 10min timelimit, so there is no danger to fry your wife or yourself from the seat.
To reach the switch inside the seat needs some fumbeling, but no special tools are reqired and no destroying tragedy danger is involved. Here what to do:
Behind seat bottom, remove 4 and 2 metal clips attaching seat leather on both side ends. This helps you unhook the black plastic strip between them stretching the seat leather. Push the plastic strip under the backrest foreward and pull it now from the front side as far as possible. Try to locate the thermoswitch in the open space. It’s inside the heater cushion fabric and should be about in the postion were I put the beerlid for the picture. When located make an apropriate cut in the fabric to get access to it. The 2 wires to the switch are slide-on connectors. Just pull’em and take the switch out. Now up to you to “soderbridge” (as I did) the two contacts on it or connect the 2 wires in the seat cushion together.
X300 from the Spitfire factory Castle Bromwich - keep 'em roling! Chris Switzerland