mine would drift so i replaced it with a hunter from walmart. cost was ~$25. i've read that u can replace it with any that has battery backup.
i'll see if i can find the wiring diagram for it. i can remember that Rh and Rc are connected to common. there is a 7.5v line that isn't used.
we were on the road half the summer and had no problems with the replacement.
the other thing is that the hi and low fan both connect to the fan terminal. u loose the ability to switch from high to low fan...it stays on hi. i didn't use the low speed anyway. u can solve that with an external switch.