All great ideas. Thank you very much. I contacted Thetford and they said it's a bad controller. I looked at other posts and a controller gone bad seems to be common with this toilet. In fact, Thetford said that they added a sensor, I think in 2006, that detects if the toilet is flushed repeatedly and will shut off power to the toilet. This prevents the toilet from overflowing and damaging your rig with toilet water and possibly sewage. In my opinion, this is a band-aid to the real problem which is a controller that goes bad.
When I called Thetford, they initially quoted me a price for a new controller of $54. They then transferred me to another individual to finish the order and the price became $178. I'm not going to pay $178 for a new controller, especially since it's just a replacement part and prone to go bad again in the future. I'm going to replace the x#!!% toilet with another brand that is more reputable than a Thetford product. I also have the Norcold refrigerator, made by Thetford, that had a recall because in propane mode the refrigerator could overheat and burn your rig down. Thetford, in my opinion again, applied a band-aid to the problem and installed a sensor that turns the refrigerator off if it gets too hot.
You can be sure that my next rig will be Thetford-free.