Ezgo won't run

[JohnnieB]

Originally Posted by Bmw2074

Re: 91 marathon controller
Ok so far I have completed the following test on my cart.

1. Pot box wires show 0-7.9 ohms as I push the gas down. Pot box ohms move smoothly from 0-7.9 and there is no jumping.

2. Pack voltage is at 38 after a day or so of not being charged.

3. I put the multimeter on the packs main neg terminal then took the positive lead and placed in on the M- on my controller. With the cart on, and the F-R switch in F, I then hit the gas until the solenoid clicked. Voltage was 0 at M- before I hit the gas, but once I hit the gas my voltage at M - was 38V.

4. After noticing that my voltage was at full pack voltage on the M- terminal, I then gradually pressed down on the gas to see if my voltage dropped down to 0. Upon pushing the gas down, the lowest my voltage got to was 33 volts. It never dropped all the way down to zero..

5. Attempted to trace the high current circuit by putting negative terminal on the multimeter on the main pack negative, and then moving the positive to the M-, C and B on the F/R switch, then the S1,S2,A1, A2 on the motor, then the control side of the solenoid, the and finally to the battery side of the solenoid. The test was done by pressing down on the gas until the solenoid clicked, and then reading the voltage at all the points.. The result as are as follows:

M- = 38
C. = 38
B. = 38
S1. = 38
S2. = 38
A1. =38
A2. =38
Control side of solenoid = 38
Batt side of solenoid read 38 volts constantly without having to press down on the gas. When I did hit the gas I got 37.5.

Ok I got all this data and no clue how to interpret it. I have read on this forum that test 3-4 indicates that my control box or my pot box are bad. Can anyone please help me to determine what I need to do or what exactly is going on with my cart. Money is tight right now, so I don't want to waste it on parts that I don't need and that might not fix my problem.

Thanks again for any and all your help.

1. You have some Pot Box issues, but the symptoms they will cause are different than the symptoms being reported.
Basically, with a 0 to 7.9K pot reading, the cart would work normally until pedal was depressed about 3/4 the way to floor and than die.
Nominally, the pot should read 50 Ohm or less with pedal at top and 300 ohms or less when the solenoid first clicks.
It should increase smoothly as pedal is slowly pressed. Smoothness easier to observe on a analog or needle type ohmmeter, but digital will work if pedal is depressed very slowly.
Ohmic value should be between 4.5K to 5.5K when pedal reaches floor. If ohmic value exceeds 7.0K. the controller will think the Pot Box has failed or has been disconnected and shut off.

2. Good.

3. When the solenoid first clicks, you should have full battery pack voltage at M-.

4. Voltage at M- should decrease to zero or very near zero when throttle input reaches the 4.5K to 5.5K range.
I'm not sure what the voltage would be if the ohmic value at the throttle input exceeds 7.0K.

5. The first voltage reading is the significant one. If you have full battery pack voltage at M- when solenoid first clicks, you will have full battery pack voltage at the other test points listed.
However, if you don't have full battery pack voltage at M- when the solenoid first clicks, there will be a bad cable, component or connection someplace between M- and the main positive terminal on battery pack. That is when time to go looking for the problem at the other test points, otherwise they are redundant.

-------
The high pitched squeal you are hearing is the pulse frequency the controller uses.
The out of the controller to the motor isn't actually DC, it is Pulsed DC. More correctly, it is Pulse Width Modulated (PWM) DC.
Basically, the current control element in the speed controller is a dozen or more Metallic Oxide Semiconductor Field Effect Transistors (MOSFET) That are switched on and off about 15,000 time a second. How long the stay on determines how much current flows through the motor.

The actual pulses are from about zero to full battery pack voltage and their duty cycle varies between 0% and 100% depending on the throttle input to the controller. When measured with a voltmeter, the pulses are averaged, so the reading you get will be from zero to full battery pack voltage.

--------------

Bottom Line:
Your cart has two problems.
A. Pot Box. Might just be out of adjustment or might be wrong/bad pot. (This is something to address after cart is running)
B. Controller. Probably has several blown MOSFETs.
I'm basing this on the fact that the cart will turn its wheels when they are off the ground, won't move cart when setting still, but will propel cart if given a push.
In other words, the controller will supply a little current to the motor, but not a lot.
All the evidence points to a bad controller, so if it were my cart, I would replace it.

[Bmw2074]

Thank you very much johnnieB B for all your help. In reference to the pot box, I think it was just out of adjustment. I took it off and adjusted the lever so that it reads about 5k at almost full throtle. I will start looking for a new controller now and once I get it running I will look at the pot box more to see if it needs to be replaced.

Thanks again for all the help.

Sent from my SAMSUNG-SGH-I747 using Tapatalk 2