75ZT Community

Can anyone describe to me the wiring of the heated seat switches in the central console?
What currents, where the feed comes from, use of relays etc. that sort of thing.

many thanks...

Quite complex, really for what they do.

The basics are this. The whole seat heating is fed from the ignition switch. There's a contact which is switched on with ignition, but switched off again when starting the car, to relieve load on the battery.

This feed goes to the switch to supply the electronics, and also directly to the seat heaters.

The other end of the seat heaters is connected to the seat heaters switch, and the switch connects this to ground, using electronics, to switch the heater on.

The electronics in the switch do a couple of things. If the voltage is low, the heaters are switched off so they don't work when the engine isn't running, and in any case, they switch off after a time interval.
There are no external relays involved in this, so the heat switches have two big terminals to carry that current.

Inside the seats, attached to the heating element, there's a thermostat. When the temperature reaches a preset level, the heating is switched off, regardless of the switch being on. Some people have changed the thermostat for a higher temperature version because they don't think the standard one gets warm enough.

I'm not sure of the actual current taken by the heaters, so can't advise on that.

Just to close this, got this working with the following setup:
feed from 50A towbar to:
1 30 amp fuse to:
1 relay, powered by towbar ignition feed to earth in passenger A pillar earth to:
1 four way fuse box, 4 x 15 amp fuses fitted to:
4 wires, 2 to each seat, 1 for electric motors and 1 for heated seats.
The earths from the seat motors went to the earth under the central console behind airbag ecu
the earth from seat heaters went to the heated seat switches and back to the earth under the central console.
the green light feed for the switches came from the towbar ignition feed.
the illumination feed for the switches came from the cigarette lighter illumination feed. (I have removed the cigarette lighter completely now - just have facia now with nothing behind it. Why would you want to have a fag in my lovely car? Plus it was useless for running sat nav etc. Now have proper aux socket in front ashtray run from the cig lighter power. Much better.)

all wiring came from panel under glovebox, to central facia and under central console, then underneath seats.

and everything works fine.

PS the relay setup feeds from the ignition, so no power without the ignition on...