good pot box good batteries still only goes slow or cuts out

[jereosbou]

got this 93 cart from a guy a while back just now getting to work on it.
guy had put an upgraded 3.5hp 3000 rpm buggies motor in it and had had a local golf cart shop "convert" the stock controller to 400 amps. said he had an alltrax but since it didnt fit in stock space he decided to go back to stock. idiot lol. anyway he said he was having problems with the pot box as he could go slow but it cut out at higher speeds but if he played with it it would finally run full throttle. i assumed it was potentiometer and since he didnt have batteries in it when i got it i didnt test it . well ordered new pot box without testing old one because im stupid. now turns out i have the same sort of problem. if i give more then the tiniest bit of throttle it cuts out power to the motor. i messed with things and found out if my pot puts more then 500 ohms not 5000 500 then it cuts out. so i adjusted my pot to only put that out at full peddle pressure just to see if it would maintain running at that ohms level and it will i made a couple loops around my house at 1/16th mile per hour and it never cut out. turn the pot box up the slightest bit though to even 550ohms and controller will cut out until you let off the peddle close the microswitch and depress it again.
did all the checks they sat to do on here for controller all voltages read right. even the no runaway on the peddle works right. ie if you had peddle down and turn on key it wont go let off peddle and press again and it will smoothly accelerate.

is my controller bad? am i missing something to check? all connections are fresh clean and tight.

im guessing youll tell me controller is bad. should i get this one rebuilt? buy a new one?

budget is a concern so am interested in cheaper route. somewhere between cruising as is at 1/16th mph and 450.00 for alltrax controller.

thanks for help in advance.

[scottyb]

Are you sure you have a controller that is compatible with the pot output. There are 0-5k pots and 5k-0 pots and 0-5k,5k-0, voltage reading, and ITS reading controllers. Sounds to me like you have been given a mismatch. My advice is call the shop & take it back.