[havasusteve03Beast]

Before you flame and prompt me to search, my problem is different than those discussed in previous threads. I could not find any posts that reported a similar issue.

I recent attempted to turn on my heated seat for the first time this year and got no response from either the driver or passenger button. No lights, no heat. They have both worked without issue in the past. No blown fuses or other issues during my 18 months of ownership.

I have power to fuse #32 and the fuse is not blown.

I have power to the Sport and DSC buttons as they both function.

A search on realoem turned up nothing. What do I look for next as I don't know what other component could be involved?

Adam,

I know its unlikely that both are bad, but have you check power to the back of the switch(s)?

 

[Clemster]

Adam,

I know its unlikely that both are bad, but have you check power to the back of the switch(s)?

I haven't. Not sure if the all switches in this housing are fed by one supply. If not which of the dozen or so wires is the power supply to the seat heater switch or switches?

A wiring diagram would help. Where might I find that?

 

[Clemster]

Looked here...
[URL="http://spaghetticoder.org/bmw/wds/e39new/"]http://spaghetticoder.org/bmw/wds/e39new/[/URL]





Found this...

The last part seems relevant.

Seat heating

The seat heating system heats the seat cushion area and backrest. The electronics for controlling the selected heating temperature (3 stages) and fault monitoring are integrated in the switch centre of the centre console.
Function

Seat heating can be switched on in three heating stages as from terminal 15 by pressing the button. Three LEDs built into the switch centre light to indicate operation. "Terminal 15 active" is signalled to the centre console switch centre via the K-bus.
Initially, heating stage 1 is activated when the seat heating is switched on (button pressed once). The seat surface is heated up to approx. 44 °C. All three LEDs light to indicate operation.
By pressing the button once more, the topmost LED goes out and heating stage 2 is activated. The seat is now only heated up to 39 °C.
The seat heating system is switched to heating stage 3 by pressing the button once again. The bottom-most LED lights. The seat is heated up to 35 °C.
The seat heating is switched off by pressing the button once again or switching off the ignition. The seat heating can also be switched off in any heating stage by pressing the push button for longer than 1 second.
The seats are heated by means of carbon fibre heating mats in the main section and steel wires (steel filaments) in the bolster. A carbon fibre heating mat is installed in both the seat cushion section as well as in the backrest. The centre sections of the seat and backrest as well as the bolsters of the seat and backrest are always heated. Heating filaments or carbon fibre mats are additionally integrated in the thigh support on sports seats. The seat and backrest bolsters are not heated on the series E39 sports seat with fabric cover.
The temperature is measured by a temperature sensor in the seat upholstery and passed on to switch centre.
Monitoring functions

Battery voltage

The electronic seat heating control switches off the power supply to the heating mats if the battery voltage in the vehicle is less than 11.4 V ±0.3 V. The function LEDs however remain on. Power supply to the heating mats is restored when the battery voltage is greater than 12.2 V ±0.3 V for at least 5 seconds.
PC-Board temperature

Due to the fact that the power input of the seat heating system is very high (120 W), the temperature of the pc-board in the switch centre is monitored by temperature sensors. Initially, the heating power is reduced as the temperature increases to over 85 °C. The heating is switched off if the pc-board temperature exceeds 95 °C. The function LEDs however remain on. The seat heating cuts in automatically again when the pc-board temperature drops below 85 °C.
Fault monitoring

The electronic seat heating control system monitors the temperature sensor and heating mats for faults. Detected faults are stored in the fault code memory of the centre console switch centre.
The following faults can be recognized:

• Short-circuit or line break
• Short-circuit or line break of temperature sensors
• Break in heating mats

If a break or short occurs at the temperature sensor, the seat heating is switched off in order to prevent overheating. The function LEDs are switched off.

 

[E55AMG2]

Battery Voltage could very well be the culprit. Put the car on a 10A tender and see if they function.

 

[Clemster]

Battery Voltage could very well be the culprit. Put the car on a 10A tender and see if they function.

This would make sense except that the LED's should be lit even though no heat is generated. I get no lights at any point.

 

[mattmartindrift]

batteries can do weird things to digital controls. make sure you've got ~12v @ the battery with the car OFF. Also, possible ignition switch symptom:

1999 528i electrical issues - Bimmerforums - The Ultimate BMW Forum

 

[Clemster]

Interesting and helpful, Matt. My OEM battery is about 18 months old, but about a month ago I came out to a car that would not start. Beginning of an FSU problem? Or did I leave an interior light on for days? I did NOT get 12v with the car off. More like 10.8V which seems odd as my car starts right up. No more assumptions...I'll throw a charger on it today.

 

[mattmartindrift]

10.8 defnitely seems low.

 

[mattmartindrift]

apparently, the ignition switch can also cause some battery draining in E38s:

BMW E38 Battery Drain

 

[ssomed]

Carbon Fiber

I am so telling my ricer friends that my car is so cool it has carbon fiber in the seat heaters!

ssomed

 

[Clemster]

I checked voltage this morning at 11.73V before connecting the charger. After charging for 45 minutes I had the other Matt check for function in my absence. Still nothing. I will have battery and charging system checked to see if there is a problem. Seem like a logical starting point?

 

[E55AMG2]

This would make sense except that the LED's should be lit even though no heat is generated. I get no lights at any point.

The LED is wired to the heater circuit. No power, no LED.

 

[Vector57]

I checked voltage this morning at 11.73V before connecting the charger. After charging for 45 minutes I
had the other Matt check for function in my absence. Still nothing. I will have battery and charging
system checked to see if there is a problem. Seem like a logical starting point?

With 11.73 volts, the battery is gone. Replace it and check alternator with engine operating; should be
between 13.5 - 14.5 volts.

Regards,
Alan

 

[chowdah]

Hi Adam, when my OE battery was dead/dying its engine-off voltage was 11.9. That was at the typical ~6yr fall-off-a-cliff timeframe (for OE). My notes say my new battery was 12.7 at engine-off.

 

[Clemster]

With 11.73 volts, the battery is gone. Replace it and check alternator with engine operating; should be
between 13.5 - 14.5 volts.

Regards,
Alan

After sitting in the cold garage all day off the charger, resting voltage was 12.18.

With engine idling, voltage is steady at 14.07.

Battery seems to be toast although running voltage is mid range.

Hi Adam, when my OE battery was dead/dying its engine-off voltage was 11.9. That was at the typical ~6yr fall-off-a-cliff timeframe (for OE). My notes say my new battery was 12.7 at engine-off.<!-- google_ad_section_end -->

Hey Frank,

Thanks for checking your notes. It appears that in terms of voltage, my battery is much closer to a dead one than a new one. It's also much closer in age to new than it is to 6 years.

Although just 18 months old and with approx. 12K miles, it's time for a new one. Now, to find out why...

 

[Twomanybeers]

How many miles on the car?

 

[Clemster]

How many miles on the car?

57K

 

[mattmartindrift]

I feel that i'm now invested in this, and my stubborness is going to drive me to figure it out.

from the WDS

Centre Console Switch Centre

Depending on equipment, he centre console switch centre contains the push buttons for seat heating, roller sun blind, active seat, park distance control (PDC), Electronic Damper Control (EDC), ASC/DSC and Hill Descent Control (HDC). The electronics for controlling the seat heating, roller sun blind and active seat is additionally integrated in the switch centre.

Scope of function

General

The switch centre has diagnostic capabilities. Communication takes place via the K-bus. Faults in the area of the seat heating, roller sun blind and active seat are stored in the fault code memory. In addition, the inputs and outputs of the systems can be read out or activated via the diagnosis function.
Electronics


The switch centre contains the electronics for controlling and regulating the seat heating, roller sun blind and active seat.

• Seat heating: Temperature control of seat heating in three preselectable heating stages, fault monitoring.
• Roller sun blind: Activation of roller sun blind drive after pressing corresponding push button, fault monitoring.
• Active seat: Activation of active seat after pressing corresponding push button, fault monitoring.

Push buttons

The push buttons for PDC, EDC, ASC/DSC and HDC have no connection to the electronics of the switch centre.
Variants

In view of the various vehicle equipment, there is a large variety of variants for the centre console switch centre. The switch centre does not feature the electronic control on vehicles not equipped with seat heating, roller sun blind and active seat. In this case, the system does not have diagnostic capabilities.

 

[mattmartindrift]

also, the pinout for the switching centere plug:

A169 Switching centre

Plug connector overview

<TABLE border=1 cellSpacing=0 cellPadding=5><COLGROUP><COL width=70><COL width=70><COL width=311></COLGROUP><TBODY><TR><TH>Number</TH><TH>X-pin, colour</TH><TH>Description</TH></TR><TR><TD>X1869</TD><TD>23-pin, Black</TD><TD>Plug connector Switching centre</TD></TR></TBODY></TABLE>
Pin assignments at plug connector X1869

<TABLE border=1 cellSpacing=0 cellPadding=5><COLGROUP><COL width=34><COL width=34><COL width=187><COL width=198></COLGROUP><TBODY><TR><TH>Pin</TH><TH>Type</TH><TH>Description / Signal type</TH><TH>Connection /
Measuring notes</TH></TR><TR class=pinrow1><TD>1</TD><TD>A</TD><TD>Signal, seat heating on</TD><TD>Heated seats</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>2</TD><TD>E</TD><TD>Voltage supply, terminal 15</TD><TD>Fuse F17</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>3</TD><TD>E</TD><TD>Signal, terminal 58g</TD><TD>Connector, terminal 58g</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>4</TD><TD>E</TD><TD>Signal, driving dynamics</TD><TD>DME control unit</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>5</TD><TD>E</TD><TD>Signal, driving dynamics</TD><TD>DME control unit</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>6</TD><TD>M</TD><TD>Ground</TD><TD>Ground connector</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>7</TD><TD>E</TD><TD>Voltage supply terminal 30</TD><TD>Fuse F32</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>8</TD><TD> </TD><TD>Not used</TD><TD> </TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>9</TD><TD> </TD><TD>Not used</TD><TD> </TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>10</TD><TD> </TD><TD>Not used</TD><TD> </TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>11</TD><TD> </TD><TD>Not used</TD><TD> </TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>12</TD><TD>A</TD><TD>Temperature signal, seat heating</TD><TD>Heated seats</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>13</TD><TD>A</TD><TD>Signal, seat heating on</TD><TD>Heated seats</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>14</TD><TD>A</TD><TD>Signal, sun blind Up</TD><TD>Sun shades motor</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>15</TD><TD>A</TD><TD>Signal, sun blind Down</TD><TD>Sun shades motor</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>16</TD><TD>A</TD><TD>Signal, DSC passive button</TD><TD>ABS/DSC control unit</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>17</TD><TD> </TD><TD>Not used</TD><TD> </TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>18</TD><TD> </TD><TD>Not used</TD><TD> </TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>19</TD><TD>M</TD><TD>Ground</TD><TD>Ground connector</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>20</TD><TD>A</TD><TD>Signal, sun blind</TD><TD>Roller sunshade remote control switch</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>21</TD><TD>E/A</TD><TD>K-bus signal line</TD><TD>K-bus connector</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>22</TD><TD>A</TD><TD>Temperature signal, seat heating</TD><TD>Heated seats</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR><TR class=pinrow1><TD>23</TD><TD>E</TD><TD>Voltage supply terminal R</TD><TD>Fuse F45</TD></TR><TR class=pinrow2><TD colSpan=2> </TD><TD> </TD><TD> </TD></TR></TBODY></TABLE>