EZ go just stops with slight hum when pedal is down

[usdiehls]

With batteries fully charged, my EZ go's power will just disapear. When you press the pedal, the motor hums with a barely noticeable vibration. Seems to be trying to push forward. While towing it back to the house, my daughter kept trying the pedal and BAM, it starts working again so she drives it home. The next time we take it out, it runs for a few minutes then loses power again. One day last week I took all the cables off and cleaned connections and reconnected. I drove it for about 10 minutes and tried everything to make it stop working, including driving over bumpy terrain at full speed. It worked great. Put it back in garage and charged batteries. The next day my daughter rode it and didn't even get out of the driveway. Batteries seem to charge fully. Any help would be greatly appreciated and my 12-year-old daughter will have her "wheels" back. Thanks in advance.