a serial number of this truck would be a good thing, and would help us give you more correct information
as for bypassed controller,,, I don't think so, (but it is a w.a.g. without the serial number). I think a 66 can also be a bad motor, motor brushes, cable loose, or controllers needing to be setup, but without the serial number to know which controllers you have, it's all just w.a.guessing
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