OK I lifted up the back wheels and traced the throttle wire and brake wire. With the remaining 2 plugs
1. I unplugged both and both motors run
2. I plug in one, left side sensor, and both motors run
3. I plug in one, right side sensor after disconnecting step #2, and only the left motor runs.
What specific part number should I order?
Those test results indicate that the right side sensor is faulty. Our item number for the right side sensor is TRX-RSWITCH which is located on our TRX parts page at this link: https://www.electricscooterparts.com/trxelectricscooterparts.html
Also, here is a direct link to the product page for the TRX-RSWITCH:
Scooter did not work. Replaced the batteries and scooter throttle shows red light power and green light full. Raised rear wheels and applied throttle and left motor runs. Right motor does not start. When riding the scooter gets to about 5mph it feels like it will go faster then cuts out. You can then reapply throttle when it stops and same result.