Here's a procedure I used. With this and a volt meter I was able to figure it out. I used different thermostats that I got on Amazon for $19 each (I have two)
http://www.modmyrv.com/2012/01/03/mo...tal-thermostat
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Remember to leave the switch set for oil/gas heater. Not Heat Pump. 7.4 volt is not used. I am installing small voltage regulators to replace the batteries. These are available from model airplane sources. They are known as 3.3v UBEC.
Sudsy