Quote:
Originally Posted by derbo
Quote:
Originally Posted by wyatth
That much is beyond me.
I really want to add heat and go with airbag models but this sounds like a ballache. Maybe I should KISS.
|
It's a simple relay circuit 
the heater circuit's main power is connected to the battery, and the relay switch power source is the 12V switched power source which is the cigarette lighter circuit.
This allows the seat to draw more wattage while allowing the circuit to use a 12V switched source as the trigger. It's a standard textbook relay circuit that should be pretty easy to implement.
Now the OEM heater circuit, since there are 3 modes, I wonder if it is a PWM circuit or just 3 different step voltages to let the heater module do the work. I'll have to look if I can find some information on it on TIS.
Edit:
Quote:
Seat heating (E8x and E9x from 09/2009, E7x) and active seat heating (E7x only)
Seat heating and active seat ventilation in front
If the seat heating/active seat ventilation button is pressed, the IHKA control unit sends the status as a K‐CAN message.
Depending on the equipment specification of the seat, the message is received either by the seat modules or by the Junction Box electronics (JBE).
Message direct to the seat modules:
The seat heating and the active seat ventilation are actuated by the respective seat module according to the operating logic at the IHKA control panel.
Message via Junction Box electronics:
The Junction Box electronics transmits a message to the seat modules in the form of a pulse-width modulated signal (PWM signal). The seat heating is actuated by the respective seat module according to the operating logic at the IHKA control panel.
If the energy management system requires a reduction in output, the heater and blower output may be reduced in 3 stages or switched off completely:
Heating and blower output are reduced from level 3 to level 2
Heating and blower output are reduced to 50 percent of level 2
Seat heating and active seat ventilation are switched off
|
|
So where are you grabbing 12v? In the glove box fuse?