Alltrax XCT 1 Green/1 Red Open/Short Circuit

[MauiHoss]

I have a 2002-5 (tag missing) PDS 36V EZGO with an Alltrax XCT controller.

One day everything is fine, the next day it's not. This is pretty much always the case with problems that are reported on forums (LOL).

Checked the blink codes on the controller -- 1 Green/1 Red indicating an open/short circuit. Started researching here on BGW to look for answers.

• Wires on the output side going to the motor all seems to be in good condition -- no rub through at the usual places.
• With all wires disconnected from the motor, there is no continuity between any A and F terminal.
• Did a motor ohm test based on ScottyB's troubleshooting aids with the following results:
  • A1-A2 = 24.7-24.8 BAD (this is way out of range)
  • F1-F2 = 1.1-1.3 OK
  • F1-motor case = 5.7 OK

I replaced the brushes on this original motor in January of 2018 -- about 18 months ago now.

Is my motor toast?

[MauiHoss]

Just checked for continuity between the motor terminals (all wires removed from the motor).

A1-A2 -- no continuity
F1-F2 -- continuity present

So I guess that could mean a couple things. Maybe one of the brushes is stuck or maybe the connection between the terminal and the brush is broken.

Would seem that I need to pull the motor apart to appraise the situation. Still, I wonder, based on what I've found with the ohm test, if the motor is toasted? I suppose that either way, I'm going to need to pull the motor.

[Sergio]

That last test you had "F1-motor case = 5.7 OK", it is not OK, there should be no continuity between any motor posts and the case.

Taking the Motor apart would be the only way to evaluate the problem.

[MauiHoss]

Interesting. So I guess ScottyB should update his Troubleshooting Aids & Tips page which says the following:

MOTOR TEST Ω ohms
This method requires checking the windings with an OHM meter
Check ohms between a1 and a2 .3 to 1 ohm.
check f1 to f2 -1 to 2 ohms.
check a1 to f1 should be open.
check f1 to casing of motor s/b > then 5 ohms.

[JohnnieB]

Originally Posted by MauiHoss

Interesting. So I guess ScottyB should update his Troubleshooting Aids & Tips page which says the following:

MOTOR TEST Ω ohms
This method requires checking the windings with an OHM meter
Check ohms between a1 and a2 .3 to 1 ohm.
check f1 to f2 -1 to 2 ohms.
check a1 to f1 should be open.
check f1 to casing of motor s/b > then 5 ohms.

Scotty definitely needs to proofread that page.

Here is how it should read:

CHECK MOTOR WINDINGS:
Set your VOM to RESISTANCE (Ω).
With your motor disconnected, measure A1 to A2. This must measure BETWEEN .3Ω and 1Ω.
With your motor disconnected, measure F1 to F2. This must measure BETWEEN 1Ω and 2Ω.
With your motor disconnected, measure A1 to F1. This must measure OPEN.
With your motor disconnected, measure F1 to motor case. This must measure greater than 5MΩ.

5MΩ is shorthand for 5,000,000Ω. Ideally it should be open, but over time the entire interior of the motor case gets coated with carbon dust from the brushes and some undesired conduction does occur.

[MauiHoss]

Thank you for the clarification on checking motor windings JohnnieB.

I took the motor out and pulled the armature with end-cap. Everything looked OK. All of the brushes seemed to be in contact. No obviously damaged wiring. Put it back together then retested A1 to A2 and to my surprise it was in range! Put the motor back in the cart and retested with the VOM only to find it was again out of range but not much. Figured I would wire it up and see what happens. I still have an open/short -- 1 red/1 green.

It's about this time that I was thankful for the diagnostic red/green blinking LED on the Alltrax controller. I would have preferred that the problem was fixed but nice to have confirmation either way.

I took the motor apart again and had a closer look. Still nothing obvious since I don't really know what I'm looking for. With the armature/end cap set on end - cap side down/armature up vertical - I held the VOM leads to A1 and A2 while slowly turning the armature through 90 degrees. In that 1/4 turn the ohms went from normal 0.3 into the 1000's and back to normal. This happened every 90 degrees of turn.

What the heck does that mean? Is the motor a goner?

[yurtle]

I'm late here, but did you try, I don't know, actually cleaning the commutator and measuring the brushes for excess wear? In the manual.

[MauiHoss]

Thanks yurtle. I installed new brushes a little over a year ago so they should be fine. When I did that, I cleaned up the commutator but it's a good idea to clean it again. I'll see if that changes anything and report back.

[yurtle]

Originally Posted by MauiHoss

Thanks yurtle. I installed new brushes a little over a year ago so they should be fine. When I did that, I cleaned up the commutator but it's a good idea to clean it again. I'll see if that changes anything and report back.

OK. I can imagine worn brushes and/or commutator causing the symptoms you mentioned, but not if they're "new" and commutator was "recently" cleaned. Unless you drive yours a LOT, I'd consider a year ago to be "recent". You can inspect where the internal conductors connect to the studs. Also, make sure the brush/spring/holder assembly works correctly; sliding back and forth easily without binding or turning sideways. Do the brushes appear to be wearing evenly; not more on one side than the other?

Finally, the commutator has wires connected to each conductive "strip". See if any of them look bad. I've seen motors (not golf cart) where some of the strips came loose.

[Sergio]

Originally Posted by MauiHoss

.....
I held the VOM leads to A1 and A2 while slowly turning the armature through 90 degrees. In that 1/4 turn the ohms went from normal 0.3 into the 1000's and back to normal. This happened every 90 degrees of turn.

What the heck does that mean? Is the motor a goner?

Make sure all four brushes are properly connected, you may want to pull on each of the brushes wires to make sure they are not broken or disconnected.