Resistor Coil on Fire!

[Grumpa]

Grandson two came to me announcing that Grandson one was driving the golf car (861/2 ezgo electric) and it was moving by itself with the key off. I went to investigate and found the resistor coil assembly on fire. After quickly removing all the cables from the coil it took a fire extinquisher to put out the fire. What caused this? And what should I check/replace in addition to the resistor assembly?

[golfcartg]

That’s no fun at all! Fires like that can be scary, especially when they happen out of the blue, but let’s break down what might have caused this and what to look for. The resistor coil system on your 1986.5 E-Z-GO cart is an older type of speed control system. Instead of a modern controller, your cart uses a series of large resistors to regulate speed. When you drive at lower speeds, the coils heat up as they dissipate excess power. The slower you go, the more the resistors heat up because they’re taking on the extra load that’s not being used by the motor. This system was cost effective and worked for its time but can be prone to overheating, especially under certain conditions.

Given that the fire occurred in the resistor coil assembly, one likely cause could be extended low speed driving. If your grandson was driving around slowly for a long period, those resistors would have been working overtime to burn off the excess energy. Since the coils can only handle so much heat, prolonged low speed operation can cause them to overheat and potentially catch fire, especially if airflow around the resistors is blocked or the wiring has any issues. It’s also worth considering that a mouse nest or some other debris could have built up around the coils, insulating them and preventing proper cooling, which can accelerate overheating.

The fact that this happened after your grandson drove it suggests that driving habits might have played a role. If you’ve been using the cart without issues until now, and the problem arose only during his use, it’s possible that he was simply driving at low speeds for too long, causing the system to overheat. However, it’s also wise to inspect the wiring for any signs of wear, fraying, or improper connections, as faulty wiring can lead to shorts or excessive resistance, which would also overheat the coils.

In addition to replacing the resistor coil assembly, I’d recommend checking the solenoid as it plays a key role in this system. The solenoid switches the power on and off to the resistor coils, and if it’s sticking or malfunctioning, it could cause the cart to behave as you described, moving without the key on, which could contribute to overheating. Also, thoroughly inspect the wiring harness for any signs of damage or corrosion that might have caused the issue. Once the new resistor assembly is in place and possibly a new solenoid, make sure the area around the coils is clean and free of debris, and keep an eye on driving habits, especially when it comes to prolonged low speed driving. This should help prevent future overheating problems.

Im attaching the wiring diagram to this message for reference, if you have any questions feel free to ask!