Likely you have corrosion in the system. there is a black control box under the left step. Many wires go to this. it needs to be taken off, under the control box is a white circuit board, here you will find the corrosion. you will need to clean or repair by soldering jumper wire across the corroded circuits.
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.