Rough/Jerky Start

[elstevo109]

I just picked up my first cart at an auction last week. Its a 1987 Marathon in pretty rough shape. The wiring is mostly intact, although there is some corrosion on the wire ends. I put 3 12v batteries in it to test the cart before I commit to buying new 6 volts. I drove it around the yard a couple times today before stopping. A few questions for you guys.

The motor works in both forward and reverse, but the throttle seems very touchy. It acts as though there is only stopped or full speed. If I try to ease onto the pedal the cart will jerk off to a start, not smooth at all. I've never driven an electric cart before. Is this normal?

I also noticed a hot wire between the selector switch and the solenoid. I didn't find any other hot wires. But the second wire going to the resistor had melted some of the insulation near the end at one point in time.

Thanks for any help

[rockfordpi]

Originally Posted by elstevo109

I just picked up my first cart at an auction last week. Its a 1987 Marathon in pretty rough shape. The wiring is mostly intact, although there is some corrosion on the wire ends. I put 3 12v batteries in it to test the cart before I commit to buying new 6 volts. I drove it around the yard a couple times today before stopping. A few questions for you guys.

The motor works in both forward and reverse, but the throttle seems very touchy. It acts as though there is only stopped or full speed. If I try to ease onto the pedal the cart will jerk off to a start, not smooth at all. I've never driven an electric cart before. Is this normal?

I also noticed a hot wire between the selector switch and the solenoid. I didn't find any other hot wires. But the second wire going to the resistor had melted some of the insulation near the end at one point in time.

Thanks for any help

Check out the wiring diagram at this link.

http://www.buggiesgonewild.com/elect...g-manuals.html

Speed is controlled by the amount of voltage to motor. Voltage is varied by the resistor bank, which reduces voltage from battery pack as current flows through it.

The greatest voltage reduction occurs when current flows through the entire length of resistor bank (accelerator switch position 1). As you press accelerator to position 2, current flows through less of the resistor (voltage drop is less) and cart goes faster. At position 4, current is not going through resistor at all (max speed, full pack voltage to motor).

So, speed is not going to be smooth, basically you have 4 speeds and cart will travel at one of those speeds.

From here you should be able to troubleshoot the issue and see if your speed situation is normal or there is an issue.

[BobBoyce]

Originally Posted by elstevo109

I just picked up my first cart at an auction last week. Its a 1987 Marathon in pretty rough shape. The wiring is mostly intact, although there is some corrosion on the wire ends. I put 3 12v batteries in it to test the cart before I commit to buying new 6 volts. I drove it around the yard a couple times today before stopping. A few questions for you guys.

The motor works in both forward and reverse, but the throttle seems very touchy. It acts as though there is only stopped or full speed. If I try to ease onto the pedal the cart will jerk off to a start, not smooth at all. I've never driven an electric cart before. Is this normal?

I also noticed a hot wire between the selector switch and the solenoid. I didn't find any other hot wires. But the second wire going to the resistor had melted some of the insulation near the end at one point in time.

Thanks for any help

Those resistor carts were ok for what they were designed to be used for. If you intend to rebuild the cart as original, it may be hard to find decent replacement parts for the resistor pack. You might want to consider updating it to a newer solid state speed controller. It will be more gentle on the motor and batteries to have a smooth application of current rather than the jerky steps that the resistor speed controller doles out. And it'll get more range per charge as well when driving at partial speed.

[elstevo109]

Thanks for the help. So I should be able to be measure the resistance or voltage drop coming out of the resistor bank. Does anyone have resistance numbers available that I can compare too? I'll start doing research on the solid state conversion as well.

[rockfordpi]

Originally Posted by elstevo109

Thanks for the help. So I should be able to be measure the resistance or voltage drop coming out of the resistor bank. Does anyone have resistance numbers available that I can compare too? I'll start doing research on the solid state conversion as well.

Yes, you could measure the voltage at each switch position in the bank and that controls your speed.

I don't have those numbers, but I am not sure they will help you that much. I think the resistor either works as designed or it does not. The important thing is that it starts low and incrementally increases at each step.

I have seen instances where people have bypassed section(s) of the resistor (usually to get around a bad solenoid on resistor carts with a different design). Be sure that has not happened.

Though I still enjoy playing with these and making them work (I am kind of Nostalgic that way), and they do have a certain beauty in their simplicity, as Bob said, these are very inefficient. With a resistor cart, you use the same amount of power (AMPS) when going slow as you do wide open. When the resistor lowers the voltage, it creates heat which is energy loss.

Scotty b., site sponsor here, sells some nice upgrade kits. Not sure how things are in your market or what shape your cart is in, but in my area people usually come out better selling the older cart and buying a newer one as opposed to upgrading a resistor to a Solid State Controller.

[elstevo109]

I measured voltage going to the motor at each of the 4 steps last night. With power coming from the first step in the accelerator voltage was reduced to about 34 volts. Wide open throttle produced 37.5v at the motor. Is it safe to assume there should be more reduction thru the resistor?

[rockfordpi]

Originally Posted by elstevo109

I measured voltage going to the motor at each of the 4 steps last night. With power coming from the first step in the accelerator voltage was reduced to about 34 volts. Wide open throttle produced 37.5v at the motor. Is it safe to assume there should be more reduction thru the resistor?

Yes.

Are you measuring the voltage for each step (switch position) at the end of the resistor (or switch point 4) on the diagram?

If so, how many ohms do you get across the full length of the resistor, end to end.

[elstevo109]

Yes I measured voltage from each step at position 4 on the resistor bank. I will measure the ohms this afternoon and post the results.

Thanks

[elstevo109]

Figured out the problem and thought I would update. The problem ended up being that the copper contacts in the speed control had arced together. So no matter where the pedal was it would send the power thru wire 4 straight to the motor. Cart is fixed and driving great now. Thanks for all the help