Seat Heater Mat Faults - Further Diagnostic Guidance

Advice On Pinpointing Which Heater Mat Is Faulty - Diagnosis Of Seat Heater Elements Using Resistance Measurements Of Backrest Heater Mat - In the case of suspected seat heater element failures, the exact location of the failure (seat cushion or backrest heater element) should always be confirmed by electrical resistance tests before replacement. Do not replace components based only on temperature performance. Heater mat failures can be located through resistance measurements of the backrest heater mat (Note: the resistance of the seat cushion heater mat cannot be measured directly because one pin is hid by the seat cushion cover over the unit). Use the following procedure to check the resistance of the backrest heater mat:
- Disconnect the backrest heater mat.
- Use a digital multimeter to measure the backrest heater mat resistance @ 20°C (note: this should not be done when the seat heaters have been used recently, as a previous heating cycle can increase the resistance leading to an inaccurate reading).
- Refer to the table below for expected resistance values. If the measured resistance is outside this tolerance, then replace the backrest seat heater mat. If the resistance is within the specified tolerance, the seat cushion heater mat should be replaced.
Seat Heater Sensor Faults - Each seat has two heating elements: one in the base (seat cushion), and one in the back (backrest). There is only one heater sensor in each seat, which is located in the base. This sensor controls both heating elements. If there is a fault with the sensor signal, neither element will operate. If the signal fault is traced to the sensor itself (in the seat cushion heater mat), there is no need to replace the backrest heater mat.
Simultaneous Failure of Both Seat Heater Mats Is Unlikely - The seat cushion and backrest seat heater elements connect to the HVAC Control Module, but the control module only acts as a splice box and the elements are electrically wired in series (each drawing proportion of battery voltage). The only way for one element to operate while the other is faulty is if one is the elements has a short-circuit fault. Under normal circumstances, where short-circuit faults are present these will be detected by the HVAC Control Module which will switch off both elements. Similarly, if the sensor (in the seat cushion element) is faulty, the HVAC Control Module will not apply voltage to the elements and, if one element is open-circuit, then no voltage can be supplied to the other element. Given this, while it may often be the case that both elements cease to operate, it is extremely unlikely that both heater mats are faulty. Consequently, if a fault is confirmed with one of the seat heater mats, do not also replace the other.

VEHICLE/MY	SEAT ROW	CUSHION ELEMENT PART NUMBER	SEAT BACK ELEMENT PART NUMBER	HEATER MAT RESISTANCE		HEATER MAT OPERATING CURRENT DRAW AT 13.5 VOLTS
VEHICLE/MY	SEAT ROW	CUSHION ELEMENT PART NUMBER	SEAT BACK ELEMENT PART NUMBER	Cushion Circuit Ω/°C	Seat Back Circuit Ω/°C	Cushion Circuit Amps/°C	Seat Back Circuit Amps/°C
XJ/X351 15-19MY	Row 1	7W93-F603B26-A	7W93-F648A40-A	2.51 Ω +/-10% @ 20°C	1.62 Ω +/-10% @ 20°C	3.24 A @ 20°C	3.24 A @ 20°C
XJ/X351 15-19MY	Row 2	FW93-F638B34-A	FW93-F668A80-A	1.32 Ω +/-10% @ 20°C	1.10 Ω +/-10% @ 20°C	5.49 A @ 20°C	5.49 A @ 20°C
F-TYPE/X152 15-17MY	Row 1 RH	EX53-603B26-B	EX53-648A40-A	1.37 Ω +/-10% @ 20°C	0.54 Ω +/-10% @ 20°C	6.92 A @ 20°C	6.92 A @ 20°C
	Row 1 LH	EX53-603B27-B	EX53-648A40-A	1.37 Ω +/-10% @ 20°C	0.54 Ω +/-10% @ 20°C	6.92 A @ 20°C	6.92 A @ 20°C
	Row 1 RH SSSS	EX53-603B26-B	CW8M-C648A22-A	1.37 Ω +/-10% @ 20°C	0.54 Ω +/-10% @ 20°C	6.92 A @ 20°C	6.92 A @ 20°C
	Row 1 LH SSSS	EX53-603B27-B	CW8M-C648A22-A	1.37 Ω +/-10% @ 20°C	0.54 Ω +/-10% @ 20°C	6.92 A @ 20°C	6.92 A @ 20°C
F-TYPE/X152 18-21MY	Row 1	JX53-603B26-A	JX53-648A40-A	1.31 Ω +/-10% @ 20°C	0.77 Ω +/-10% @ 20°C	6.37 A @ 20°C	6.37 A @ 20°C
XF/X260 16-20MY	Row 1	GX73-603B26-A	GX73-648A40-A	0.86 Ω +/-10% @ 20°C	0.70 Ω +/-10% @ 20°C	8.65 A @ 20°C	8.65 A @ 20°C
XF/X260 16-20MY	Row 2	GX73-600D76-A	GX73-601C30-A	1.76 Ω +/-10% @ 20°C	1.12 Ω +/-10% @ 20°C	4.69 A @ 20°C	4.69 A @ 20°C
XE/X760 16-20MY	Row 1	GX73-603B26-A	GX73-648A40-A	0.86 Ω +/-10% @ 20°C	0.70 Ω +/-10% @ 20°C	8.65 A @ 20°C	8.65 A @ 20°C
XE/X760 16-20MY	Row 2	GX73-600D76-A	GX73-601C30-A	1.76 Ω +/-10% @ 20°C	1.12 Ω +/-10% @ 20°C	4.69 A @ 20°C	4.69 A @ 20°C
F-PACE/X761 17-20MY	Row 1	GX73-603B26-A	GX73-648A40-A	0.86 Ω +/-10% @ 20°C	0.70 Ω +/-10% @ 20°C	8.65 A @ 20°C	8.65 A @ 20°C
F-PACE/X761 17-20MY	Row 2	HK83-600D76-A	HK83-601C30-A	1.57 Ω +/-10% @ 20°C	0.97 Ω +/-10% @ 20°C	5.31 A @ 20°C	5.31 A @ 20°C
Range Rover Velar/L560 18-22MY	Row 1	J8A2-603B26-A	J8A2-648A40-A	1.38 Ω +/-10% @ 23°C	0.95 Ω +/-10% @ 23°C	5.79 A @ 23°C	5.79 A @ 23°C
Range Rover Velar/L560 18-22MY	Row 2	J8A2-600D76-A	J8A2-601C30-A	1.64 Ω +/-10% @ 23°C	1.21 Ω +/-10% @ 23°C	4.74 A @ 23°C	4.74 A @ 23°C
I-PACE/X590 18-20MY	Row 1	GX73-603B26-A	GX73-648A40-A	0.86 Ω +/-10% @ 20°C	0.70 Ω +/-10% @ 20°C	8.65 A @ 20°C	8.65 A @ 20°C
I-PACE/X590 18-20MY	Row 2	J9C3-600D76-A	J9C3-601C30-A	1.48 Ω +/-10% @ 20°C	1.02 Ω +/-10% @ 20°C	5.40 A @ 20°C	5.40 A @ 20°C
I-PACE/X590 21MY	Row 1	GX73-603B26-A	GX73-648A40-A	0.86 Ω +/-10% @ 20°C	0.70 Ω +/-10% @ 20°C	8.65 A @ 20°C	8.65 A @ 20°C
I-PACE/X590 21MY	Row 2	M9D3-600D76-A	J9C3-601C30-A	1.48 Ω +/-10% @ 20°C	1.02 Ω +/-10% @ 20°C	5.40 A @ 20°C	5.40 A @ 20°C
Range Rover Sport/L494 18-20MY	Row 1	JK62-603B26-A	JK62-648A40-A	1.11 Ω +/-10% @ 20°C	0.95 Ω +/-10% @ 20°C	6.43 A @ 20°C	6.43 A @ 20°C
Range Rover Sport/L494 18-20MY	Row 2	JK62-600D76-A	JK62-601C30-A	3.40 Ω +/-10% @ 20°C	0.95 Ω +/-10% @ 20°C	3.08 A @ 20°C	3.08 A @ 20°C
Discovery/L462 17-20MY	Row 1	HY32-603B26-A	HY32-648A40-A	0.94 Ω +/-10% @ 20°C	0.69 Ω +/-10% @ 20°C	8.08 A @ 20°C	8.08 A @ 20°C
	Row 2	HY32-600D76-B	HY32-601C30-B	1.81 Ω +/-10% @ 20°C	1.04 Ω +/-10% @ 20°C	4.67 A @ 20°C	4.67 A @ 20°C
	Row 3	HY32-600D76-A	HY32-601C30-A	1.58 Ω +/-10% @ 20°C	0.97 Ω +/-10% @ 20°C	5.21 A @ 20°C	5.21 A @ 20°C
Defender/L663 20MY	Row 1	L8B2-603B26-A	L8B2-648A40-A	1.38 Ω +/-10% @ 23°C	1.06 Ω +/-10% @ 23°C	5.57 A @ 23°C	5.57 A @ 23°C
	Row 2 Fixed	L8B2-600D76-C	L8B2-601C30-C	1.50 Ω +/-10% @ 23°C	1.87 Ω +/-10% @ 23°C	4.00 A @ 23°C	4.00 A @ 23°C
	Row 2 TAS	L8B2-600D76-A	L8B2-601C30-A	2.06 Ω +/-10% @ 23°C	1.36 Ω +/-10% @ 23°C	4.03 A @ 23°C	4.03 A @ 23°C
	Row 3	L8B2-600D76-B	L8B2-601C30-B	1.90 Ω +/-10% @ 23°C	2.85 Ω +/-10% @ 23°C	2.92 A @ 23°C	2.92 A @ 23°C
Range Rover Evoque/L538 16-19MY	Row 1	GJ32-603B26-A	GJ32-648A40-A	1.12 Ω +/-10% @ 20°C	0.81 Ω +/-10% @ 20°C	6.99 A @ 20°C	6.99 A @ 20°C
Range Rover Evoque/L538 16-19MY	Row 2	GJ32-600D76-A	GJ32-601C30-A	1.58 Ω +/-10% @ 20°C	1.14 Ω +/-10% @ 20°C	4.96 A @ 20°C	4.96 A @ 20°C
E-PACE/X540 18-20MY	Row 1	GX73-603B26-A	GX73-648A40-A	0.86 Ω +/-10% @ 20°C	0.70 Ω +/-10% @ 20°C	8.65 A @ 20°C	8.65 A @ 20°C
E-PACE/X540 18-20MY	Row 2	J9C3-600D76-A	J9C3-601C30-A	1.48 Ω +/-10% @ 20°C	1.02 Ω +/-10% @ 20°C	5.40 A @ 20°C	5.40 A @ 20°C
Discovery Sport/L550 15-17MY	Row 1	FK72-603B26-A	FK72-648A40-A	1.25 Ω +/-10% @ 20°C	0.96 Ω +/-10% @ 20°C	6.00 A @ 20°C	6.00 A @ 20°C
Discovery Sport/L550 15-17MY	Row 2	FK72-600D76-A	FK72-601C30-A	1.86 Ω +/-10% @ 20°C	1.24 Ω +/-10% @ 20°C	4.30 A @ 20°C	4.30 A @ 20°C
Discovery Sport/L550 18-19MY	Row 1	JK72-603B26-A	JK72-648A40-A	1.25 Ω +/-10% @ 20°C	0.96 Ω +/-10% @ 20°C	6.00 A @ 20°C	6.00 A @ 20°C
Discovery Sport/L550 18-19MY	Row 2	JK72-600D76-A	JK72-601C30-A	1.86 Ω +/-10% @ 20°C	1.24 Ω +/-10% @ 20°C	4.30 A @ 20°C	4.30 A @ 20°C
Discovery Sport/L550 20MY	Row 1	K8D2-603B26-A	K8D2-648A40-A	1.13 Ω +/-10% @ 20°C	0.81 Ω +/-10% @ 20°C	6.96 A @ 20°C	6.96 A @ 20°C
Discovery Sport/L550 20MY	Row 2	JK72-600D76-A	JK72-601C30-A	1.86 Ω +/-10% @ 20°C	1.24 Ω +/-10% @ 20°C	4.30 A @ 20°C	4.30 A @ 20°C
New Range Rover Evoque/L551 19-20MY	Row 1	K8D2-603B26-A	K8D2-648A40-A	1.13 Ω +/-10% @ 20°C	0.81 Ω +/-10% @ 20°C	6.96 A @ 20°C	6.96 A @ 20°C
New Range Rover Evoque/L551 19-20MY	Row 2	K8D2-600D76-A	K8D2-601C30-A	1.14 Ω +/-10% @ 20°C	0.75 Ω +/-10% @ 20°C	7.14 A @ 20°C	7.14 A @ 20°C