I did this mod and it works great!! It keeps the TT a more constant temp and with out the big temp swing before the AC/HEAT turns on or off.
You do need to be a little bit mechanically inclined because it is not a direct wire for wire transfer and you need to modify the thermostat and add a micro switch to control the fan speed (HI/LOW).
My unit on the TT is a Colman and I used the Hunter thermostat, I used this article during my mod maybe it can help you with your trouble shooting. Also check you batteries to make sure they have a good charge still in them, I have heard of that causing strange effects on the system. Good Luck.