Discovery I (LJ) V8-4.0L (1996)
/v8-4.0l/Page-2485001.png)
Seat Heater: Description and Operation
Electric Seats
Description
The heated seat elements for each seat are supplied power from a seat heat module located on the underside of the seat frame. The seat heat module
provides consistent temperature control of the seat heater elements. A negative temperature coefficient variable resistor is located in the seat cushion
heater element. The resistor changes its resistance as the seat cushion temperature increases or decreases. The resistance is monitored by electronics
within the seat heat module, which raises or lowers the power supplied to the elements and controls the element temperature between 26 and 36 °C (79
and 97 °F).
The heated seat elements are operated by a latching seat heater switch for each seat located in the center console between the two rear window switches.
The heated seats only operate when the ignition switch is in position II.
Circuit Supply
A feed from the battery positive terminal is connected on an R wire to the engine compartment fusebox where it passes through fusible links 1, 5, 7 and
8. Fusible links and 5 and 1 and 7 are connected in series.
A feed from fusible links 1 and 7 is connected to the contacts of the auxiliary circuits relay.
A feed from fusible links 1 and 5 is connected on an NG wire to connector C0255-5/C0751-1 interface. From connector C0751-1, the feed continues on
an NP wire to the coil and contacts of the LH power seat relay. The earth path from the relay coil is connected on an OP wire to the BCU pin C0663-3,
via header C0724.
A second feed from fusible links 1 and 5 is connected on an NP wire to the coil and contacts of the RH power seat relay. The earth path from the relay
coil is connected on an OP wire to the BCU pin C0663-3, via header C0724.
The BCU completes the earth path when ignition I or II or driver's door open is sensed.
A feed from fusible link 8 is connected on an NW wire to the passenger compartment fusebox and from the fusebox to the ignition switch on an N wire.
Ignition Switch Supply
With the ignition switch in position I or II the feed from fusible link 8 passes through the ignition switch to the passenger compartment fusebox on an
LGW wire.
The feed continues through fuse 26 in the passenger compartment fusebox and is connected from the fusebox on an LG wire to the coil of the auxiliary
circuits relay in the engine compartment fusebox. This feed energizes the relay coil, closing the relay contacts. The relay coil is earthed on a B wire, via
header C0286 LHD/CO288 RHD, to earth header C0018.
Operation
With the auxiliary circuits relay energized, the feed from fusible links 1 and 7 passes through the relay contacts and is connected to the passenger
compartment fusebox on a WG wire where it passes through fuse 15.
From the passenger compartment fusebox, the feed is connected to header C0761 on an LGW wire. From the header C0761, the feed separates into two
LGW wires which are connected to the LH and RH seat heater switches.
From the LH seat heater switch the feed is connected on a US wire to connector C0225-1/C0751-1 interface. From connector C0751-1 the feed continues
on an OW wire to the LH seat heat module.
From the RH seat heater switch the feed is connected on a UK wire to connector C0253-1/C0751-1 interface. From connector C0751-1 the feed
continues on an OW wire to the RH seat heat module.
Power is supplied to the electronics within the LH or RH seat heat module by the feed from the LH or RH seat heater switch. This allows the feed to pass
through the module and is connected to the LH or RH seat cushion heater on a K wire. The LH or RH seat squab heater is connected in series from the
LH or RH seat cushion heater on a KW wire. The LH and RH seat squab heaters are connected to earth header C0708 on B wires via splice joint 1.
The earth from the LH or RH seat heat module is connected on an LG wire to a temperature variable resistor contained within each of the LH and RH
seat cushion heaters. As the temperature of the seat cushion heater increases, the resistance of the resistor changes. This is sensed by the seat heat module
which varies the power supplied to the LH and RH seat cushion heaters, raising or lowering their temperature accordingly.
The resistors are connected to the LH and RH seat heat module on B wires and from the LH and RH seat heat modules to earth header C0708 on B wires
