I converted mine too to scotchbrite but still use the fluid. No mess at all. With the higher voltage is spins nicely. I am saying that I cant turn the speed control on or off with the cleaner car connected no matter if the cleaner is on or off. Pull the cleaner off the track and the MTH speed control turns on and off using the buttons, no dcs.
Maybe the speed control isn't working. Excessive drag could cause a problem as well I suspect, I don't do much running in conventional mode. Any of my full sized diesels or steamers can tow this cleaner with no issues. AAMOF, I've towed this and another cleaning car together at times.
As an aerotrain, it works fine. I can turn the speed control on and off an when it goes around curves, it slows down and starts up again.I have noticed though that it starts up in slow mode. All of my other MTH engines start normal speed.