EZGO Marathon Slows To Nothing

[pjmia96]

I have a 1991 EZ-GO Marathon Electric all 4 Gauge Wiring. Brand New 6 Volt Battery's. It wont take off on its own or it needs to be already rolling down a hill to take off. When it takes off it runs fast on flat pavement, or on pavement with a slight incline (As long as the Pedal is to the Floor) if you go on grass on flat ground/or up a bumpy hill that is not pavement it slows down to a crawl and dies. To get it going again it needs to be already moving then you need to floor it and stay on the pavement. When it is on the flat Pavement you need to get a head start on flat road and it will drive up the pavement hill fine if you are going fast enough and the pedal is to the floor it has plenty of power.

TROUBLESHOOTING

1. 40 Volts with Battery's fully Charged.

2. Voltage drops to 39v under a load.

3. Solenoid clicks every time.

4. Runs when already rolling and eventually slows down to nothing.

5. All wire connections are clean tight and in the right place.

6. When checking voltage between m- and b- when the solenoid clicks I get the total pack voltage (40 Volts) and as I push the pedal the voltage drops to 0 so that tests good.

7. When testing voltage between m- and b+ when the solenoid clicks I get 0 volts and as I push down the pedal it rises to the full pack voltage as I slowly push the pedal down. So that tests good.

8.When testing the pot box the voltage rises from 0 to 6k and as I pushed the pedal the voltage bounces all around.

9. F&R works fine

10. Micro switches are fine.

11. New solenoid.

12. Motor Changed in 2003

How do I fix This

Thanks,

Matt

[gaminde]

I would start with motor brushes, Is this a controller cart or resistor cart.

[gaminde]

Number 8 in your testing You're saying voltage but you're giving resistance measurement, And if it bounces around its most likely bad, now you have 2 things to check

[pjmia96]

It is a controller cart (Numbers 6 and 7 are controller tests)

I have a new pot coming this week. Sorry about test number 8, I set my digital tester to 20k and tested pot box continuity and the reading bounces around(especially) at full throttle between 0 and 6 on my digital meter.

[pjmia96]

The controller seems to test just fine. So it is either the pot box or the motor. I think what it might possibly be is when the pot box reading bounces around it is sending false readings to the controller and it doesn't know what to send to the motor. But the cart runs fine when its off the ground. When the pedal is to the floor the cart does not cut out but the cart wont go any faster unless the cart is already moving. Also, when the cart is on the ground it takes off faster at half throttle then full throttle.

What do you think,

Thanks,

Matt

[pjmia96]

OK I have a Brand New Digital Multimeter that I just Bought yesterday. Today I will Test the voltage at the motor as the pedal is pushed. I still need to install my New Pot Box but I will do that this weekend depending on if the part shows up at my house or not.

I cant wait to fix this Problem,

Thanks,

Matt

[gaminde]

OK I have a Brand New Digital Multimeter that I just Bought yesterday. Today I will Test the voltage at the motor as the pedal is pushed. I still need to install my New Pot Box but I will do that this weekend depending on if the part shows up at my house or not.

I cant wait to fix this Problem,

Thanks,

Matt

I would be very interested in seeing how the motor ohms out as it's being rotated And input voltage to the controller as your pressing the peddle. Now voltage at the motor may not be correct using the DC scale as you are pulsing with a frequency and dc is a flat wave So also try with the AC scale and see how the voltage readings compare.

[pjmia96]

I have all the Controller Tests Listed above. The Output test is listed on my first post.

Matt

[pjmia96]

OK, These tests were done with the Cart on the ground. When I press the gas pedal with the Cart in Forward or Reverse and I am on the Flat Lawn the cart will not take off on its own without being on flat pavement, or being pushed and jumped on when on the lawn. When you press the gas pedal to go forward it tries to go but just sits there so I figured I was safe. I took some Different Motor Tests.

A1-S2 Forward=3.2 Volts
A1-S2 Reverse=2.6 Volts
A1-S1 Forward=2.8 Volts
A1-S1 Reverse=2.8 Volts
A2-S2 Forward=0.5 Volts
A2-S2 Reverse=0.2 Volts
A2-S1 Forward=0.3 Volts
A2-S1 Reverse=0.5 Volts

I noticed when I tested Voltage between A2 and B+ on the Controller with the cart on the ground this time with the cart having no power to move on its own and with the Pedal to the Floor I get 3.0 Volts in forward at full throttle and 2.7 in reverse at full throttle, that is the power coming from the controller and going to the motor. I also noticed that I get different results when testing with the cart on the Ground then on Jack stands. Testing voltage between M- and B+ on the controller with the cart on the ground I get 0 Volts at solenoid click and 3.5 volts at full throttle. When the cart is on Jack stands the voltage is 38 Volts and the wheels spin like crazy. Should I do all my PREVIOUS tests (Not These) from the beginning with the Cart on the ground.

I would think on the ground I should have the same results as the cart being on jackstands?

What do you guys think,

Thanks,

Matt

[gaminde]

OK, These tests were done with the Cart on the ground. When I press the gas pedal with the Cart in Forward or Reverse and I am on the Flat Lawn the cart will not take off on its own without being on flat pavement, or being pushed and jumped on when on the lawn. When you press the gas pedal to go forward it tries to go but just sits there so I figured I was safe. I took some Different Motor Tests.

A1-S2 Forward=3.2 Volts
A1-S2 Reverse=2.6 Volts
A1-S1 Forward=2.8 Volts
A1-S1 Reverse=2.8 Volts
A2-S2 Forward=0.5 Volts
A2-S2 Reverse=0.2 Volts
A2-S1 Forward=0.3 Volts
A2-S1 Reverse=0.5 Volts

I noticed when I tested Voltage between A2 and B+ on the Controller with the cart on the ground this time with the cart having no power to move on its own and with the Pedal to the Floor I get 3.0 Volts in forward at full throttle and 2.7 in reverse at full throttle, that is the power coming from the controller and going to the motor. I also noticed that I get different results when testing with the cart on the Ground then on Jack stands. Testing voltage between M- and B+ on the controller with the cart on the ground I get 0 Volts at solenoid click and 3.5 volts at full throttle. When the cart is on Jack stands the voltage is 38 Volts and the wheels spin like crazy. Should I do all my PREVIOUS tests (Not These) from the beginning with the Cart on the ground.

I would think on the ground I should have the same results as the cart being on jackstands?

What do you guys think,

Thanks,

Matt

I'm looking at your tests A to S and wondering where you came up with them?
and what results were you expecting.

[gaminde]

One more time disconect the wires going to A1 and A2 with batteries disconnected, put your meter on ohms connect to A1 and A2 with cart on jack stands rotate motor slowly and check for Resistance !

[pjmia96]

Changed the Pot Box it didn't fix it.

I have determined that it needs a new Controller so I have a brand New 300 Amp Alltrax coming this weekend.


We should be good to go but we will see when I put in the new Controller this weekend.

Thanks,

Matt