A3 8P seat heater control

[Alex1337]

Hello. I have a question about the way how electric seat heaters work. At Audi A3 8p 2007.

 

I have a retrofit project. I'm trying to install Audi front seats into other car. I have only the seats and no climate control unit. I'm trying to emulate the seat heater control unit. I don't need the heating levels. Just turning it on and off is enough.

 

At the seats I have three wires: seatbelt indicator, airbag and heater. The heater connector has 10 possible pins and 4 wires used. Two of them are thick and other two are thin. The thick ones are Brown and Black-Green and thin ones are Brown-White and Black-White. Unfortunately I couldn't understand the wiring diagram. I assume that thick wires are + and – for heater. And thin wires are the thermo resistor (heat sensor) or something like that. Just applying +12 V and ground to the thick wires (ground to Brown and +12 V to Black-Green) does not make seat heater work. I was trying to short-circut the thin wires or apply an adjustable resistor up to 10 kOhm to these wires but there's no result. But if I connect +12 volt through the stop lamp it lights up to 50% so there's some small consuming at the two thick wires. I used the multi tester to measure and I got like 0,5 A consuming at the thick wires. This looks like I have heaters working at the lowest level. I also applied the multi tester in the circuit mode and seems like thick wires circuit is not broken (also it as resistance between wires). But the thin wires circuit it not beeping on circuit test and has no resistance (on both seats).

 

Is there any option to make seat heater work properly (no need of levels, just MAX heat, I will control it with buttons and relay)? What do I have to connect to the thin wires (Brown-White and Black-White)?

 

I understand that I can disassemble the seats and connect +12 V to the heater unit directly. But I don't want to disassemble the seats if there's any other better way to emulate the heater control unit.