controller fried? no B+/M- voltage

[damon561]

1994 ezgo, not sure of model ( custom body) , series motor. Cart will drive fine for a few minutes in the morning , then clicks but won't move - if you let it sit for an hour or so it will repeat. nothing is getting hot and I have done the ITS test which shows correct voltages. Battery voltage is 38.1, individual all over 6.2, solenoid showing good according to troubleshooting charts.The only thing I can find troubleshooting is very low ( .5-1V ) voltage at B+ to M- terminals - according to troubleshooting chart that indicates a bad controller. I pulled the case off the controller and see nothing obviously fried and no corrosion- I am assuming one or more failing Mosfets but can't find anywhere to buy those (PMC-NE8d) . It is a 4 post controller .... Am I correct about the controller? Any suggestions for Mosfets or am I stuck buying a controller?

[JohnnieB]

If the voltage between M- and B+ only goes up to about 1V with pedal on floor and the ITS checks good, then the controller is most likely bad. There is a slight chance of the solenoid contacts being bad and full B+ not getting to the controller.

I prefer measuring between the controller's B- and M- terminals since that measurement eliminates everything except bad controller or bad throttle. Ought to have full battery pack voltage when pedal is pushed just far enough to make solenoid click and then the voltage should decrease to zero as pedal is pressed to floor.

There are people that play with controllers that post in other BGW forums. Maybe they have some info about the MOSFETs, if that is the problem.

If your DIY thoughts don't pan out, replace it with an Alltrax SR48400 (or larger) user programmable controller.

[damon561]

thank you JohnnieB B- to M- is full voltage but does not decrease - not sure what that means - if it means new controller any suggestions on where to purchase?

[JohnnieB]

Originally Posted by damon561

thank you JohnnieB B- to M- is full voltage but does not decrease - not sure what that means - if it means new controller any suggestions on where to purchase?

The speed control valve (MOSFETs) is physically located between B- and M- and you'll see pack voltage dropped across it when it's at 0% duty cycle and zero volts dropped across it when it's at 100% duty cycle. If that doesn't happen, either the throttle is bad and not telling the controller to pass amps to the motor, or the controller is bad and not doing what it is being told to do by the throttle.

I got my upgrades here: https://www.cartsunlimited.net/alltrax-sr-series--.html

[JohnnieB]

Clarification on the B- to M- test.

If you don't get full battery pack voltage when pedal is pushed just far enough to make solenoid click, then there is a problem in the high amp cables, contacts, connections or battery pack or motor that needs further troubleshooting.

If you do get pack voltage, but it doesn't decrease when pedal is pushed, then the problem is either the throttle or controller.

[damon561]

Thanks again for the help - sounds like the controller- I am assuming the ITS is good since the voltage tests all work- thanks for the link- looked around a bit - I guess thats your place....

[JohnnieB]

Originally Posted by damon561

Thanks again for the help - sounds like the controller- I am assuming the ITS is good since the voltage tests all work- thanks for the link- looked around a bit - I guess thats your place....

I have no financial affiliations with Carts unlimited, or any other vendor, except buying stuff from some of them.

[damon561]

ok - sorry for the assumption