2009 Yamaha electric cart bucks at speed

[Jpfisher15]

I have a 2009 Yamaha electric golf cart that bucks when at full throttle. Also, the voltage meter shows that the voltage fluctuates. I replaced speed sensor but it didn’t work. Any ideas?

[cgtech]

What are you referring to as the speed sensor? The throttle position sensor, or the motor rpm sensor?

Go push your cart around manually, does the reverse beeper sound & the cart resist pushing? (That will verify if the motor rpm sensor is working).

[Jpfisher15]

Thanks for the reply. I’m referring to the motor RPM sensor. I pushed cart and got resistance. The reverse beeper, beeped on and off when I moved the cart in either direction. (Not the normal solid reverse tone like when you’re backing up in the cart. Not sure that this matters.) I’ve already load tested each battery and they are all ok.

[cgtech]

Ok, that test went perfectly normally. Your tach sensor is not the problem.

Does this occur at max speed, or only under real hard acceleration?

[Jpfisher15]

It starts out at max speed only. Then, after a few minutes of driving it occurs at all speed ranges and sometimes the cart will not move when you hit the throttle. When this happpned to me I toggled the switch from run into tow then back to run and it moved again but still bucked. I have a digital battery meter installed on the cart. When it’s bucking the battery power is all over the place.

[cgtech]

Pull & inspect motor brushes. I bet they all messed up.

[Jpfisher15]

Ok, thanks for the help!