adding heated seat pads to non heated seats

So anyone who's seen my previous posts will know I'm after a ford performance heated seat (I've already added the wiring and hvAC in readiness) 

After looking at the circuit diagram I could see the heated seats are pretty basic in the fiesta, power comes from the HVAC via a main wire, a sense wire connects to a ntc thermister in the seat wiring and depending on the resistance it senses knows if to keep the supply turned on or not.

I thought hmm you can buy cheap heater pads from china, I will try and add them temporarily to my non heated half leather just to get me through the winter.

It was easier than I thought but not fully connected in the way I wanted, the heaters I originally bought have their own switch with low, medium and high settings, bought because at the time didn't think they could be fitted to the ford system.

Here's what I did to get them working, I did some tests and worked out that the sense wire puts out 5v and depending on the voltage drop turns on the power or not. Power comes on at 9kohm so I connected pin 17 on hvAC to the power on the heated pads, added a 9kohm resistor to the sense wire which is pin 30 on hvAC. 

What this does is allow me to turn off the heated seat by using the original ford button on the control pad.

Pics attached showing the fit.