My wife's tx 300 treadmill will suddenly speed up to at least twice the speed it was going one time then all of a sudden go to the other extreme and slow down to a snails pace. I have seen that other models have similar problems, but have been unable to contact Sportcraft.
Check the speed sensor is clean. Either on the plastic pulley on the front roller (under the cover) or on the end of the motor (will shroud a wheel with slots in).
If this doesn't work then you need a new motor control board.
Warren - Treadmill Repairs - 0800 069 9518
January 2012
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