Thermostat woes

Sorry - correction - there are actually six wires going into the back of the unit. Also, there is a brown wire that comes out of the wire packet from the wall, but has been snipped off and does not go into the thermostat at all. The diagram on the back of the unit seems to indicate that there is a blank spot corresponding to this wire's location. Maybe an unused wire for other models? I am sitting in the camper right now and it kicked off a few minutes ago, so I took it off the wall, manhandled it a bit, and it's back to working now, but the digital display is off. Jumped 5 degrees when I took it off the wall. Any help in getting a programmable unit installed is appreciated. I'm fine with electrical work and wiring, just don't want to go on a hunting expedition through harnesses. If I can get something that will work with the wires I have great, if not, I guess I'll wire in a toggle switch or something to bypass the thermostat.