Crown PE 4000:
drive motor pulses a few times, then smokes the motor controller

I've got a head scratcher here, looking for an assist. I have a model PE4000-60, which would travel very slowly. I checked it out and found a bad drive motor brush. No problem, replaced the brush and sent it on it's way. The next day it came back with weird travel issues. Sometimes it would plug ok., sometimes not. sometimes when I changed directions, it would keep going in the same direction. When I brought it in to troubleshoot, I noticed a humming sound from the drive motor when the handle was up and no requested travel. The humming noise was as if the drive motor was being pulsed. it would hum for a couple seconds, then stop, then hum for a couple seconds, then stop.

This happened three or four times, then the motor controller burnt up. Actual smoke coming from the controller.

everything checks clean electrically, no shorts or grounds. I put a new motor controller in and also put a new drive motor in. when I pull the handle down and the line contactor comes in, the drive motor humming sound starts again. I unplugged the truck to keep from smoking another controller.

Any ideas??
  • Posted 6 May 2017 06:26
  • Discussion started by backwater83
  • Illinois, United States
"There are more airplanes in the ocean than submarines in the sky."
Showing items 1 - 8 of 8 results.
Are you sure you got the correct drive motor? The one in the PE4000 should be a separately excided one not like the ones in PEs prior to this. You might need to recheck your part numbers.
  • Posted 14 May 2017 10:29
  • Reply by popeye
  • Ohio, United States
I thought the same thing so I took the lift motor out of the system. Disconnected the motor with the same results. The lift and drive motors are electrically clean, no grounds, no shorts.

The plugging issue is bugging me. When I change directions, the drive motor slows and then continues turning in the same direction.
  • Posted 9 May 2017 00:08
  • Reply by backwater83
  • Illinois, United States
"There are more airplanes in the ocean than submarines in the sky."
The only time I've seen a drive motor try to run on it's own was when both the lift and drive motors had shorts to ground and voltage from the shorted lift motor was entering the drive motor through the short it had to ground. Did you disconnect the cables to the lift motor?
  • Posted 7 May 2017 21:10
  • Reply by mrfixit
  • New York, United States
I've isolated the lift pump and motor. I thought one of the handle heaters may have shorted, so I removed them from the system. I disconnected the travel pot and plugged a different pot in. No dice. There is a voltage polarity diode that is wired from battery positive to the B- port on the controller. It checked good, but I swapped it out anyway. No dice. I've been working on electric forklifts for over 20 years and haven't seen anything like this before. My next step is to swap out the drive motor with another...ive already done that before so my confidence isn't high.

Thought I could tap some of the knowledge on this forum. If anyone has any ideas, I'm all ears. I'll keep you posted.
  • Posted 7 May 2017 13:14
  • Reply by backwater83
  • Illinois, United States
Ducks with a S. Pardon the filters.
  • Posted 7 May 2017 12:53
  • Reply by Yidneck
  • New York, United States
Dreamt I was fixing a machine, then came the paperwork and it turned into a nightmare.
*** to be you. Sounds like one of those....
Does it have any added on widgets or gadgets? Maybe your getting some feedback or stray volts?
Other then the controller there are no additional greenboards on this machine to cause this so next would be unplugging parts that can cause this one at a time till you find the guilty one. Check the solenoid, contactors, horn, POT and lift pump.
Please post updates cause sounds interesting.
  • Posted 7 May 2017 12:51
  • Reply by Yidneck
  • New York, United States
Dreamt I was fixing a machine, then came the paperwork and it turned into a nightmare.
I swapped drive motors during the troubleshoot. The drive motor currently installed is not the one that had a burnt brush. Both drive motors are responding the same. I also changed the arm and field leads thinking there may have been some resistance in the power cables.

So, new motor controller, motor, and motor leads.
  • Posted 6 May 2017 20:58
  • Reply by backwater83
  • Illinois, United States
"There are more airplanes in the ocean than submarines in the sky."
i would check you brush and brush spring...possible you did something wrong changing the brush??????
  • Posted 6 May 2017 14:56
  • Reply by kevin_t
  • Pennsylvania, United States

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