Sparking Controller B Lead

[Jolo]

This is a 2007 EZGO TXT FREEDOM SE 36 VOLT. The B lead from controller sparks when attaching to the neg batt terminal, the cart is not running, the Volt Gauge does not light, and the solenoid is not working. The back story involves major errors. I installed a lithium batt and the cart ran great, but the battery had a defect after two months and was replaced. Unfortunately, the replacement battery had reversed terminals, so not paying attention and assuming polarity was identical to the returned battery, I connected the cart leads wrong. That killed the cart. I installed a new controller and solenoid. The Cart ran for a week and suddenly stopped running. The original solenoid had no diode installed. The new solenoid came with one that I installed wrong because the new solenoid was marked battery on the right side terminal (the leads to the solenoid are yellow on the left and blue on the right). The Cart did not run with new controller and the new solenoid until I removed the diode. It ran for a few days with only the original resistor installed on the large terminals of the solenoid, then the cart died again.

So, the cart is dead and the B lead from the controller sparks when it is attached to the neg batt terminal. I assume I blew another controller and possibly the solenoid. I don’t know why the cart had no diode when I purchased it, but I assume it needs one and I believe the white stripe on the diode is installed on the small left side terminal on the solenoid.

I am new to the forum and appreciate any assistance that can get the cart running again.

[golfcartg]

The spark at the B- connection suggests there's a short or internal fault in the controller which can happen if the MOSFETs or capacitors inside are damaged. Running without a properly installed diode can backfeed voltage into the controller especially during shutoff which further risks damage. At this point, it's very possible the controller and solenoid are both compromised again (further testing needed), and the safest route would be to test all components individually or start fresh with confirmed wiring, correct diode orientation (stripe toward the positive trigger side), and verified battery polarity. Let me know if you have some time and need a walkthrough.