Intermittent Jerky Start - TXT Series Cart w/ Alltrax 4855 - Why?

LATrvlr

Just upgraded a TXT series cart to 48V. Everything is new except the motor (full upgrade list below).

When starting from a dead stop the cart will often smoothly accelerate beginning just after the foot pedal micro switch operates up to full speed (Wow this 48V upgrade is fast!). Sometimes however the pedal must be depressed about half way before movement begins and of course that is an eye opening launch!

Up on jack stands for diagnostics it went along with a DVM and the downloaded sticky procedure.

Every time the accelerator is depressed the voltage as measured across the M- and B+ terminals of the 4855 smoothly advances from 0 to full pack voltage (today @ 50.4V) beginning just after the pedal micro switch operates. What is happening with the jacked up wheel mimics what I experience while driving.

During most test run-ups the jacked up wheel begins spinning smoothly at around 8 to 10 volts but occasionally the voltage gets as high as 24 to 28 volts before the wheel begins to turn and when it does, it is pretty violent.

Once the wheel is turning if the pedal is let up and reapplied, it can be run very slow down to 8 volts or so and be brought back up smoothly to any speed . Occasionally when beginning to depress the accelerator the jacked up wheel will suddenly rotate less than 90 degrees at around 10 volts then stop only to later abruptly begin rotating again at between 24 to 28 volts. All this while the DVM reading is smoothly increasing proportionally to the throttle position. Depressing the accelerator fully produces the yellow light on the 4855 which indicates it is seeing the ITS signal fully open.

There is fresh oil in the rear with no signs of metal when changed. The wheels once spun to full speed smoothly coast down with no unusual noise whatsoever.

The 4855 is programmed for ITS throttle and the ITS induction core has been adjusted to provide proper travel. No error LEDs appear at any time on the controller.

A complete electronic speed control diagnostic test downloaded from the sticky area was also performed. (Results below - I assume this was originally for a 36V Curtis controller so 48V results may vary slightly?).

I'm thinking this may likely be an internal motor issue because everything else seems to test fine unless I'm overlooking something. The cart was not running well before the build as everything was bad, FNR, batteries, connectors controller etc.

Any thoughts or ideas? Is it time to send the motor off for a rebuild?


Cart Specs - 1999 TXT Series Cart

• New US 8V Batteries
• New Alltrax 4855 AXE 500A controller
• New HD FNR, Solenoid and cables from Carts Unlimited (Scotty B.)

Controller Test Results - Alltrax AXE 4855 Test Results Appear in Blue Text

ELECTRONIC SPEED CONTROL - SERIES (NON DCS)

REAR OF THE CART SECURELY ON BLOCKS OR JACK STANDS FOR SAFETY

1. Connect (-) probe of meter on Battery Pack Negative (-) post. (This probe will on the post for the rest of the testing procedures)

2. Connect (+) probe to the Battery Pack Positive (+) battery post. (This reading is the Battery Voltage and the amount of POWER TO THE CONTROLLER – 50.4V

3. NOW, Key switch ON, gear selector in FORWARD, Place the (+) probe on the battery side of the solenoid's large post (If the reading is below battery voltage, check all wiring and terminals). 50.4V

4. Place the (+) probe to the controller side of the solenoid's large post. The reading should be 3 to 5.5 volts less than battery voltage. If the reading is more than 5.5 volts less the battery voltage, the 470 ohm resistor is faulty. If the voltage is the same as the battery voltage, replace the solenoid. 50.4V – 46.0V = 4.4Vd

ITS - INDUCTIVE THROTTLE SENSOR

1. With the key switch ON - Forward direction selected - Push the Accelerator pedal just enough to activate the solenoid.

2. Install a "jumper wire" between the batteries BL+ post and the solenoid post with red wires attached.

3. AT THE SIX PIN CONNECTOR OF THE CONTROLLER
Place the (+) probe on the red wire terminal of the connector. If battery voltage is not present, the red wire between the solenoid and the six pin connector is faulty.

4. Place the (+) probe on the black wire terminal of the connector.
The reading should be slightly above 14 volts but less than 15 volts. If the voltage is not correct, the Throttle Sensor MAY be faulty. 9.1V (Is 14 to 15 volts above correct for an Alltrax 4855 or is the 9.1V acceptable?)

5. Separate the 6 pin connector (only 4 are used) between the pedal box and the controller that's located on the passenger's side of the battery compartment. If the voltage goes to 14 volts, the sensor is faulty. If the voltage remains below 14 volts, the controller is faulty. RECONNECT the 6 pin connector. 13.7V

6. Place the (+) probe on the white wire terminal of the six pin connector. Depress the pedal slowly. The reading should be 0.45 - 0.53 volts just as the micro-switch is activated. Depress the pedal slowly to full throttle. As you depress the peddle the reading should move smoothly to about 1.5 volts. If the reading is incorrect, The Throttle Sensor is defective. .2V to .5V

7. REMOVE THE JUMPER WIRE AND (-) PROBE

CHECKING CONTROLLER OUTPUT

1. Connect (-) probe to M- terminal. Connect (+) probe to B+ terminal. The reading should indicate approx. 0 volts. Slowly depress accelerator pedal. The reading should show the voltage increasing to battery voltage when fully depressed. If the voltage is at or near battery voltage and the motor is not turning, then the problem lies in either the forward/reverse switch, the wiring, or the motor. 0V - 50.3V

2. If the voltage increases by a few volts and then stops changing while the pedal is being depressed, remove the orange wire at the "Reverse Micro switch". If the voltage is not at or near battery voltage, replace the controller. If battery voltage is present, the problem lies in the reverse circuit. Re-connect the orange wire.

MOTOR UNWANTED CONTINUITY TEST

1. Disconnect all wires to the motor and label them. Make sure none of the terminals are grounded to the motor or cart (F1 terminal to motor frame)

2. You should have continuity present between F1 and F2 and A1 and A2 but NOT BETWEEN ANY A and ANY F Terminal. S1-S2= .3 ohm A1-A2= .5 ohm S1-A1= 121k ohm S1-A2= 121k ohm S2-A1= 98k ohm S2-A2= 98k ohm

3. If any of these test fail, the motor will not operate correctly.


Thanks for taking the time to view this ginormous long post!

BGW

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yurtle

Whew, that was a long post!

My first thought was the ITS, but your good trouble-shooting and excellent description will allow the experts to zero in on the real problem. The ITS results look suspect, but I'm puzzled at how your motor starts spinning at different voltages.

I also upgraded to a 4855 but didn't have any problems, so wait for the experts to come along.

Before you upgraded, did you experience anything like this? If it's the same ITS and same motor...

I assume you checked/tightened all motor connections.

LATrvlr

Thanks Yurtle! From reading posts here for months I figured the questions would be asked so I included all known facts upfront.

All connections are correct, clean and tight. The stock cart did not have this exact same issue before the rebuild but it pretty much "died" all at once when a couple battery jugs failed and the FNR smoked.

JohnnieB

If it was my motor and I had those readings, it would be on its way to Plum Quick.

yurtle

What's bad, the 100 k-ohms between the armature and field windings? When I cleaned mine up, it was full of graphite dust from the brushes. Couldn't that cause a high resistance connection between the studs and/or wires going to the armature and the brushes?

LATrvlr

Thanks JohnnieB. I'm looking at PQ's website right now. Like Yurtle I'm also curious which reading (or both) is troublesome.

JohnnieB

If you've got enough carbon dust coating the insulators on the studs that the Stator (Field) and Armature cables attached to, to reduce the isolation between the windings into the 100K range, you are also very likely to have a similar buildup of carbon dust in the grooves of the split-ring commutator and with the various Armature poles (windings) partially shorted together, the angular relationship of the magnetic fields generated by the Armature relative to those generated by the Stator will be skewed.

I'm not sure if that will cause all the symptoms LATrvlr is reporting, but it will cause some abnormal operation and reduce the motor's efficiency, thereby causing it to run hotter.

Also, the source of the carbon dust is the brushes, so they are suspects as well.

In addition, according the the first post, the motor is reacting differently when the same voltage is being applied.
Based on that alone, it would be on its way to the repair shop, if it were mine.

Note: Some guys have have successfully rebuilt their own Cart motors, but I haven't had much luck with anything other than fractional horsepower ones, so I outsource repairs on the bigger stuff.

yurtle

I didn't check continuity on mine before and after the cleaning, but my brushes were fine. I cleaned up the commutators and replaced the bearing. I was just not expecting to see that much graphite dust. Should the reading be infinity?

I agree, I was surprised that his motor started turning at drastically different voltage. It is a 1999, so it's been around the block a few times.

LATrvlr

JohnnieB, thanks for the extra details! This motor will become purple shortly......

LATrvlr

Yurtle, it was a fleet cart when I purchased it around 2005 so no doubt it has some miles on it!