1996 E38 728i - rear seat heating switch installation

Notices

Thread: 1996 E38 728i - rear seat heating switch installation

Reply to Thread
Results 1 to 9 of 9
  1. 1996 E38 728i - rear seat heating switch installation
    #1
    Platinum BFuk Member
    Car Details
    Dherm's Car Details
    Model of Car:
    728i E38 & M5 E28
    Year of Manufacture:
    1996 & 1987
    Transmission Type:
    Automatic & Manual
    Car Body Type:
    Saloon & Saloon
    Dherm's Avatar
    Join Date
    Jul 2010
    Location
    Birmingham
    Posts
    129
    Thanks
    125
    Thanked 23 Times in 22 Posts
    Hi Guys. I'm retro fitting rear heated switch to rear console in my E38 and need some help with wiring the switches. Ive managed to work out the illumination wires which are Brown and Red/Grey. I want to know which wires are supply and load please. The wires in question are as follows;
    SWITCH LEFT.
    Brown = Earth
    Red/grey = Illumination.
    Yellow/White x2 = ?
    Green/White = ?
    Yellow/Brown = ?

    SWITCH RIGHT.
    Brown = Earth
    Red/Grey = Illumination
    Yellow/Black x2 = ?
    Green/White = ?
    White/Brown = ?

    Can someone please help. I've connected the switch to battery to check and I cant seem to get the green on light to stay on for longer than 4 secs. I only want the switch to come on and stay on. just for show there are no heated seats.
    Regards. Dherm.

  2. Remove Advertisements
    BimmerForums.co.uk
    Advertisements

  3. #2
    BMW Guru
    Car Details
    mark@vorny.co.uk's Car Details
    Model of Car:
    911 C2S
    Year of Manufacture:
    2009
    Transmission Type:
    Automatic
    Car Body Type:
    Coupe
    mark@vorny.co.uk's Avatar
    Join Date
    Sep 2008
    Location
    Appleby Magna, Derbyshire
    Posts
    6,636
    Thanks
    5,139
    Thanked 3,738 Times in 2,697 Posts
    Can anybody assist the OP ?
    2013, Porsche 911 Carrera 4S, PDK, Sports Exhaust, Chrono, etc, etc

    *removed

    BFUK weekday crew

    PLEASE READ THE POSTING RULES & HOW TO CORRECT THREAD TITLES & THE SELLING RULES

  4. The Following User Says Thank You to mark@vorny.co.uk For This Useful Post:

    Dherm(26-04-2011)

  5. #3
    BMW Guru
    Car Details
    Ronnie's Car Details
    Model of Car:
    See above
    Year of Manufacture:
    Never too old, never too new
    Transmission Type:
    Always manual
    Car Body Type:
    Usually 5 doors
    Ronnie's Avatar
    Join Date
    Dec 2007
    Location
    Bournemouth, Dorset.
    Posts
    20,398
    Thanks
    6,198
    Thanked 7,052 Times in 5,322 Posts
    Have you had a look at the wiring here? http://www.bmw-planet.com/diagrams/release/en/

  6. The Following User Says Thank You to Ronnie For This Useful Post:

    Dherm(26-04-2011)

  7. Remove Advertisements
    BimmerForums.co.uk
    Advertisements

  8. #4
    BMW Guru
    Car Details
    joylove's Car Details
    Model of Car:
    328
    Year of Manufacture:
    1998
    Transmission Type:
    Manual
    Car Body Type:
    cabrio

    Join Date
    Sep 2010
    Location
    UK
    Posts
    1,500
    Thanks
    108
    Thanked 467 Times in 367 Posts
    Is it the one with the variable temperature wheel?

    Seat heat switch
    Pin assignments at plug connector X651

    Pin Type Description / Signal type Connection /
    Measuring notes
    1 E Night light signal Connector, night lights

    2 A NTC signal Driver's seat heating

    3 E Terminal 15 Fuse F32

    4 M Ground Ground connector

    5 A Signal, seat heating on Driver's seat heating

    6 Not used =pin 5

  9. The Following User Says Thank You to joylove For This Useful Post:

    Dherm(26-04-2011)

  10. #5
    Platinum BFuk Member
    Car Details
    Dherm's Car Details
    Model of Car:
    728i E38 & M5 E28
    Year of Manufacture:
    1996 & 1987
    Transmission Type:
    Automatic & Manual
    Car Body Type:
    Saloon & Saloon
    Dherm's Avatar
    Join Date
    Jul 2010
    Location
    Birmingham
    Posts
    129
    Thanks
    125
    Thanked 23 Times in 22 Posts
    Thank you guys your help has been appreciated. Ill work on the switch this weekend. Because there are no heated seats do you have any suggestions as to what to do with wires 2 and 5. will this cause a problem if I leave them unconnected? Joylove it is the one with the variable temp wheel.
    Dherm

  11. #6
    BMW Guru
    Car Details
    joylove's Car Details
    Model of Car:
    328
    Year of Manufacture:
    1998
    Transmission Type:
    Manual
    Car Body Type:
    cabrio

    Join Date
    Sep 2010
    Location
    UK
    Posts
    1,500
    Thanks
    108
    Thanked 467 Times in 367 Posts
    The seat heat switch LED will come on for 4 seconds and turn back off if there is a fault in the seat heat. This can be open, short or incorrect load. You are seeing the fault case for an open circuit.

    You can hold the button while turning on the power and the switch will flash a fault code to tell you this. The flash code is detailed in the WDS.

    Seat heating

    The cushion surfaces and backrests are heated with the seat heating system.
    Function

    The seat heating can be switched on as of terminal 15 by pressing the button. The LED integrated in the switch lights to act as a function indicator.
    The seat heating is switched off by pressing the button once again or switching off the ignition.
    The seats are heated by means of four heating elements incorporated in the upholstery.
    Cushion surface
    Seat moulding and thigh support
    Centre section of backrest
    Backrest moulding
    The electronic circuitry integrated in the switch controls and monitors the seat heating function.
    The heating temperature can be adjusted by means of a potentiometer within the range from 20 o C to 42 o C. The temperature is measured by a temperature sensor in the seat upholstery and passed on to the electronics integrated in the switch.
    The electronic circuitry controls the heating function such that the set temperature is reached in the fastest possible time. The heating capacity is then reduced.
    Note
    Current supply to the heat conductor of the seat heating electronics is interrupted if the vehicle battery voltage drops below 11.8 volts. The function LED installed in the switch however remains on. Current supply to the heat conductor is resumed when the battery voltage again reaches 11.8 volts.
    Fault monitoring

    The seat heating electronics monitors the temperature sensor and the heating elements for faults.
    If a break or short occurs at the temperature sensor, the seat heating is switched off in order to prevent overheating.
    Fault indicator

    If a fault is recognized, the function LED installed in the switch flashes for 12 seconds when the fault occurs, or, if the fault is already present, when the seat heating is switched on.
    Flash code

    A flash code shows what faults the electronic circuitry has currently detected.
    Flash code output is started by following procedure:
    Switch off ignition
    Press and hold the button for seat heating
    Switch on ignition (terminal 15) with button depressed
    Release the button and press it again briefly
    The following faults can be indicated:
    Flashing
    Defect
    Once
    Switch faulty (potentiometer or electronics) or switch overheating due to a short-circuit
    Twice
    Temperature sensor has break or short
    3 times
    All 4 heating elements broken or have a short (probably break or short in wiring harness)
    Pin 2 NTC wire is the thermometer in the seat heat pad used for temp control.

    Pin 5 is the output to the 2 pads heat lines.

  12. The Following User Says Thank You to joylove For This Useful Post:

    Dherm(26-04-2011)

  13. #7
    Platinum BFuk Member
    Car Details
    Dherm's Car Details
    Model of Car:
    728i E38 & M5 E28
    Year of Manufacture:
    1996 & 1987
    Transmission Type:
    Automatic & Manual
    Car Body Type:
    Saloon & Saloon
    Dherm's Avatar
    Join Date
    Jul 2010
    Location
    Birmingham
    Posts
    129
    Thanks
    125
    Thanked 23 Times in 22 Posts
    Thanks joylove for your time and effort for the above explanation really appreciate it.Its guys like you who make it worthwhile turning to this forum for great advice Gauging by your response I wont be able to get the lights to stay on for more than 4 secs as there is no heating element or thermometer.
    Kind regards. Dherm

  14. #8
    BMW Guru
    Car Details
    joylove's Car Details
    Model of Car:
    328
    Year of Manufacture:
    1998
    Transmission Type:
    Manual
    Car Body Type:
    cabrio

    Join Date
    Sep 2010
    Location
    UK
    Posts
    1,500
    Thanks
    108
    Thanked 467 Times in 367 Posts
    Quote Originally Posted by Dherm
    Thanks joylove for your time and effort for the above explanation really appreciate it.Its guys like you who make it worthwhile turning to this forum for great advice
    Quote Originally Posted by Dherm View Post
    Gauging by your response I wont be able to get the lights to stay on for more than 4 secs as there is no heating element or thermometer.
    This is true. You need at least one element in place. Also the pin 6 is a GND even though it's listed as N/C. You can get MQS parts from Farnell and RS.
    http://www.bimmerforums.co.uk/forum/...ectors-t73387/

    Here is my install using that switch.
    http://www.bimmerforums.co.uk/forum/...t-pics-t75728/

  15. The Following User Says Thank You to joylove For This Useful Post:

    Dherm(27-04-2011)

  16. #9
    Platinum BFuk Member
    Car Details
    Dherm's Car Details
    Model of Car:
    728i E38 & M5 E28
    Year of Manufacture:
    1996 & 1987
    Transmission Type:
    Automatic & Manual
    Car Body Type:
    Saloon & Saloon
    Dherm's Avatar
    Join Date
    Jul 2010
    Location
    Birmingham
    Posts
    129
    Thanks
    125
    Thanked 23 Times in 22 Posts
    Thanks joylove.
    Kind regards. Dherm

Tags for this Thread

View Tag Cloud

Posting Permissions
  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts