Retrofit Motorised/Heated Seats in a Restoration Project.

Thread Starter


Joined Jan 27, 2021
Hi there,

Hoping to get some direction from those wiser than me.

I've installed a driver and passenger seat from a W203 E55 AMG Mercedes in my 1991 Toyota LC80 and can't help but think my controller design is probably cave-man'esque and with the advice of a guru, there is a solution that is more efficient.

These are not the exact seats but an image I found online of the same model:

e55 seat.jpg

Each seat contains 5 motors and two heaters, I have a copy of the relevant Mercedes factory service manual which holds all the necessary schematics and have tried to keep the naming convention similar.


Tested all the motors and they work as expected. At 12V the motors come in around 10-15 A depending on position.
When initially testing with an L298N, I realised they would drag far more current than I could test with 'cheapy' drivers so just wired up a 2 relay forward-backward switch directly from a small 12V battery.

Ideally hardware would be less than 5 rocker switches and 10 relays per seat for motion control.

My thinking is:

  1. Rotary Encoder per seat to control motor selection and heater intensity.
  2. Pressing the encoder in as a button will change between seat heating and motor selection.
  3. Rocker switch per seat to control forward/reverse when motor is selected.

Rotary encoder to switch between the 5 motors by moving CW/CCW
Perhaps 5 LEDs or similar around the knob to illustrate current selection
Single Rocker switch for FWD / OPEN / REVERSE
16-Channel 12V Relay Module (see attached)
Adruino Nano or similar to communicate between the rotary selection knob and the relays.

Run both the seat and backrest heaters in parallel, I don't see any situation where one but not the other will be required.
Using the same rotary encoder and 5 LEDs around the knob for 5 positions of intensity
20/40/60/80/100% heat intensity via PWM signal to a KSJ30 SSR (see attached)

So my questions to the brains trust is -

Do you see any issues with my thinking? Is there any other method of control you would suggest? I was thinking of an FPGA given the nature of the outputs but think it might be easier for me as a newby to stick to an IDE that has loads of online assistance around it.

Can you think of any other efficient ways to control the motors and heaters? I was even thinking of ditching the rocker switch and using the push button function on the encoder to be a 'select' of sorts then CW/CCW moves the selected motor FWD/REV but the programming path seemed a bit out of my depth at this stage.

Thanks for taking the time to read and potentially help,