I have a "05" 3670RL and would like to change out the t-stat to a programable type. The back A/C unit in my rig is a Duo-Therm by Dometic (with quick cool) and the t-stat is of the same brand. The exsisting t-stat has 7.5 with a red wire, cool is yellow, furnace is white, Hi Fan is blue, fan is orange and ground is black. On my new t-stat (Honeywell) I am pretty sure what to do with all the wires R=power(7.5 wire red), W=heat(white wire), Y=cool(yellow wire) and G=fan(orange wire). The question I have is what do I do with the black ground wire and the blue hi fan wire from the old t-stat. What purpose does the high fan wire serve and will I be losing out if I do not use it? If anyone has replaced their t-stat before I would like any info that might help with this task. I have already used the advice on the extra space under the refigerator and the oven. And I went one step further and put hinges and a handle on the panel that has my winterizer stuff under it so I would not have to keep removing the screw. (I cut off the scews and glued the heads over the holes so that it would look like they are still there). I have also installed the reciever hitch on the back to haul the bikes. Great stuff on this site. Thanks to all!!!!!!