I should add that this morning it ran for half an hour with no issues at all.

I checked the connector at the hand control and I get a steady sweep of 5.xK ohms to about 125 ohms in either direction from the throttle pot and the fwd and rev switches both switch on/off properly.

Is there anything in the circuit between the fwd/rev switches in the hand throttle and the contactors that could be dropping the ball?

Thanks for your guidance with this...

No display to give any error codes... this truck doesn't even have a battery meter on the panel!

OK, with the troubleshooting... Trying to move fwd or rev, the contactors aren't pulling in at all, so I manually pushed them in and still nothing...

If I manually push in either the fwd or rev contactor, and simultaneously push in the contactor below it, the drive wheel moves correctly. Checking for voltage at all three coils, I get 0vdc off any of the three contactors when I twist the throttle either fwd or rev. So it seems like they're not getting a signal to pull in?




Thanks again for your suggestions!

(Edited to correct symptoms info)

Rob,
I sent a response to your email
It is a GE EV100 with GE contactors
You can still test the same way, or even take the steps mrfixit says to test the drive motor overall operation.
If it does not run still there may be some other problem.
Watch the display while trying to operate it and see if it shows any errors.

That model came with either a GE EV1 or EV100 control with GE contactors. A quick way to test the motor is jack the drive wheels off the ground and manually push either the forward or reverse contactor in along with the 1A/high speed contactor and the motor should run full speed. Sounds like you have a problem with the pot or the wiring to it.

Thanks for the responses guys!

The model / serial numbers are: ESC030ABN 24 SV 083 and N539187.

Armature looks pretty good for a motor it's age, I've seen a lot worse anyway. Brushes seem to move free and spring back well enough. All four brushes are about 5/8 to 3/4 inch long.

Swoop: I sent you a PM with pic of contactor... I don't see a lebel indicating a manufacturer on the contactors themselves, though the SCR and the whole panel have General Electric labels. How can I identify them?

I appreciate your help!

this truck have the cableform contactors on it?

try this trick and see if it just needs a new contactor kit
jack the drive wheel(s) off the floor
activate the drive in either direction and then wiggle the direction contactor that is pulled in and see if it takes off running. These contactors were well known for failing even though they did look ok and appeared to pull in. The armature of the contactor can get worn and hang/bind up.

I would also check the accelerator pot with a vom and make sure it has full range.
And of course double check the motor brushes, grab the leads and pull them out a bit and let them pop back in place, this will tell you if they are worn out too much or are hanging up in the brush holders. And like kevin says, look at the condition of the armature and make sure its not arc'd up and damaged. A good armature surface will have a smooth surface and be a chocolate brown color or shiny copper where the brushes ride.

What condition do the motor Brush's look like worn out are they? How about the commutator that they ride on???
What is the serial number of the truck?