Heated Sport Seat Advice Please

G

Gav897

Member
Afternoon all

My local garage, who is fantastic and competent, has been trying to fix my heated seat problem today, but have encountered problems. Bear with me on this.

I was hoping that a simple fix would be for me to change the console switch, I tried but no good.

So my local garage:

Ordered the new heater pads
Did some tests on the loom
Plugged in the new pads

Still no heat and still all three lights on then off

What they did pick up on is that the wires on the new pads don't follow a continuous colour standard all the way through the new wiring. .

On the new inter-pad connectors, there are three wires into one connector and two out, but what seems strange is that those colours don't go colour to colour.

It goes:

Brown - Green
Green - Not connected
Grey - Brown

Potentially a manufacturing error not picked up by QA? They are sending some photos to BMW for confirmation.

My next course of action in parallel this weekend, swap driver and passenger seat and see if the fault follows.

Questions are:

Does anybody have any photos of their pad wiring they can post please, more specifically the connections between back and seat pads?

Can anyone confirm the colours?

Thanks all for any help.
 
I've made some progress.

Does anybody know what this is and where it is located in the seat?

IMG_3276.PNG


I've made resistance measurements on both my good and bad seat:

Good seat is a constant 3.3k
Bad seat is in the Mohms

Any help appreciated.
 
E57a or x733 is the cushion pad
seat_heater.jpg
 
Current measurement, seat heating

The current is measured in order to be able to provide a basic statement with regard to a defect in the seat heating system.

Measurement preparation

On vehicles equipped with a switching centre in the centre console, the current is measured directly at the switching centre.
•Switch off seat heating

•Remove centre console switching centre (A169)

•Measurement is carried out with a 50 A clip-on ammeter

•Unwind insulating tape from wiring harness under seat and attach clip-on ammeter to the wire to be measures.

•Left seat heating: Measurement on HZFA wire (white/yellow, pin 1)
Right seat heating: Measurement on HZBF wire (white/green, pin 13)

•Start engine in order to ensure a system voltage of approx. 13.8 V


System voltage

If the system voltage drops below 11.4 V, the LEDs remain lit but the seat heating is switched off. The seat heating is re-activated as soon as a voltage of at least 12.2 V is permanently applied.

Measurement at DIS tester
•Select "measurement system"

•Measurement function: Current 50 A

•Measurement connection: Clip-on ammeter

•Type of measurement: Direct current =

•Measuring range: +/- 50 A

•Check system voltage with DIS tester

•Switch on seat heater on the side to be measured


Measurement evaluation

Generally applicable for all heating stages: Each heating stage has a certain setpoint temperature. The control unit attempts to reach this temperature as fast as possible. The temperature is the kept constant by means of clocking (= pulsating direct current).
•Generally, the current is approx. 10 A during the heating-up phase (at a system voltage of 13.8 V)

•The heating output is reduced on approaching the setpoint temperature. The clocking function can now be distinctly recognized, i.e. the current pulsates between 0 and approx. 10 A.

•On finally reaching the setpoint temperature, the interval of the 0 A range is extended even longer.

•If the current temperature is higher than the setpoint temperature, e.g. when, after a longer period of operation, the heating is switched back from stage 1 (3 LEDs) to stage 3 (1 LED), no current is applied until the temperature has again dropped to the corresponding setpoint temperature.


Heating-up seat

The duration of the heating-up phase is dependent on the temperature measured at the temperature sensor! The setpoint temperature is reached more quickly at high ambient temperatures (e.g. in summer) or if the seat is preheated. In this case, the clocking cuts in correspondingly earlier.

Measured power

The measured power depends on many different factors. Both the level of the system voltage as well as the type of seat installed and operation of other loads (seat heating on other side, steering wheel heating) play a significant role. The specified value of 10 A is therefore only a reference value.

Setpoint temperatures

The following setpoint temperatures are reached in the three-stage seat heating system:
•Stage 1 operation (3 LEDs lit):
The seat is heated to a setpoint temperature of 35 °C

•Stage 2 operation (2 LEDs lit):
The seat is heated to a setpoint temperature of 39 °C

•Stage 3 operation (1 LED lit):
The seat is heated to a setpoint temperature of 44 °C


Measurement evaluation
•A current of approx. 10 A is applied:
The seat heating is OK

•A current of approx. 5 A is applied:
Defect in heating mat of seat cushion or seat backrest

•No current is applied:
Defect in heating mat of seat cushion and seat backrest
 
My heated seat thread has some wiring diagrams that may be useful:
http://www.z4-forum.com/forum/viewtopic.php?f=2&t=86176&hilit=heated+seats
 
Gav897 said:
I've made some progress.

Does anybody know what this is and where it is located in the seat?

IMG_3276.PNG


I've made resistance measurements on both my good and bad seat:

Good seat is a constant 3.3k
Bad seat is in the Mohms

Any help appreciated.
Click to expand...

I would say that's the thermostat/overheat device. Not sure where it's located, maybe someone has a pic of the actual heating pads, should be a visible "lump" where this is located.

Mike
 
Thanks to everybody so far.

First of all the pads that came from BMW had indeed been manufactured incorrectly. They swapped the pins to the correct position and returned it to my local garage. Quick plug in and still doesn't work.

I'm assuming the black connectors under the seat are for the heating circuit and blue for occupancy or airbag?

Again, passenger seat works on drivers side. Driver's seat doesn't work on driver's side, so it's defo the seat and not loom.

Thanks again all. Great job on your seats Marlon.
 
Also there is a third cable on E58 that goes through what looks like the variable resistor. That isn't on the new pads from BMW and they say that it isn't needed anymore.

Really?
 
Gav897 said:
I've made some progress.

Does anybody know what this is and where it is located in the seat?

IMG_3276.PNG


I've made resistance measurements on both my good and bad seat:

Good seat is a constant 3.3k
Bad seat is in the Mohms

Any help appreciated.
Click to expand...

I realise this is a super old post - but where are people measuring the ohms of the temp signal? I tried measuring between GROUND and the GREY wire (Pin 23) as per the WDS but I don't get a reading (0ohm) yet my heated seats work perfectly. The reason I'm trying to figure out where to get the reading from is because I've fitted RX8 seats now and want to get the heater working from the OE panel - which means potentially adding an NTC Thermistor into the seats, but I can't figure out what value to go for
 
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