Clark TW40:
Forklift jumps then dies?

We have a TW40 3 wheel forklift and it devloped an issue where it jumps and then nothing. It will basically move 2 feet on the motor jump then its dead. If you try to creap it in does nothing until you are far enough in to engage the motor which dies instantly. You can still shift if forward and reverse the reverse beeper comes on. TO get it to jump another few feet you have to put it in nuetral and cycle the key on and off. We are guess it is the throttle but I am not sure what to test or check 1st. Any suggestions would be greatly appreciated.
  • Posted 16 Aug 2012 06:19
  • Discussion started by specequip
  • Michigan, United States
Showing items 16 - 30 of 94 results.
The insulation on the 3 wires going to the right front motor is spongy. I am goning to disconect these and load test them just to make sure. Also is there something that tells the right motor to turn faster then the left motor? maybe a switch on the steering or rear swingarm?
  • Posted 31 Aug 2012 06:32
  • Reply by specequip
  • Michigan, United States
It sounds like one of the SCRs is misfiring under load. In the EV1 manual look up symptoms 1E and 2B. Since the #2 and #5 are new, check the 22 and 25 RECs. Notice that it says the 25 can check good but still cause the #5 to misfire under load so that may be the next part to try. If any of the SCRs misfire it is going to shut down with the pmt, like what is happening.
  • Posted 31 Aug 2012 06:21
  • Reply by mrfixit
  • New York, United States
OK. Here is what its doing. Wheels on the ground. Forward no creep but just past 1.4 pedal it jumps and pmts. Reverse creeps for a second at 1/4 pedal then pmt's it will not move forward or reverse creep or not without PMT.
Wheels in the air. Creeps forward and reverse. High speed works as long as you don't just floor it. If you floor it it PMTs.
  • Posted 31 Aug 2012 04:36
  • Reply by specequip
  • Michigan, United States
It would be much easier to diagnose what's wrong if you explain exactly what's it doing or not doing. Does it creep at all when the petal is pushed 1/4 of the way? Forward and reverse? Does it shut itself off (pmt)? If so, what are you doing exactly when it shuts down? How does it react as you slowly press the petal down? Can you press the petal down all the way and have it click into high speed and run? Does it run differently with the wheels spinning off the ground rather than driving it? It shouldn't be difficult to figure out what's wrong but you have to be crystal clear in explaining how it is reacting while trying to drive it.
  • Posted 31 Aug 2012 04:30
  • Reply by mrfixit
  • New York, United States
Its not the card :( although I was able to get it to move a little in reverse. So maybe just a little the card. Please Tell me what to check next. I would be pulling my hair out by now but I have no hair to pull out :(
  • Posted 31 Aug 2012 04:01
  • Reply by specequip
  • Michigan, United States
I would have had you take voltage readings at the 2 term strips on the side of the card, which takes a few steps since what we would be looking for is the correct inputs to the card at the correct times, and I would have offered a quick way to bench test the SCRs to be sure they turn on and off correctly.
It may well be the card, and at least this way, the card should be eliminated as a problem.
Be sure to come on back and let us know what symptoms you have with the new card, it will likely need to be setup for this truck.
We can 'walk you through it', if you have the time to wait for a reply.
  • Posted 31 Aug 2012 03:56
  • Reply by edward_t
  • South Carolina, United States
"it's not rocket surgery"
I relize that it may not be the card. The card has corrosion on it from getting wet. The screws going into it are rusted. I have checked the SCRs and contactors. I find no shorts or chasis grounds. I am kinda at wits end. I figured for $100 why not. I just don't know what to check next at this point.
  • Posted 30 Aug 2012 22:12
  • Reply by specequip
  • Michigan, United States
I am sorry you felt like you had to get something on order, and while it is possible that your card caused the failures, it is not all that likely, for this set of failures, and more likely that your card is working correctly to prevent other problems like a run away condition, when it senses something else not working correctly.
  • Posted 28 Aug 2012 20:05
  • Reply by edward_t
  • South Carolina, United States
"it's not rocket surgery"
Yes I didn't relize they where cables. There are 4 on the left side facing forward and 3 on the right side. I tested each of them to chasis and found nothing. Then I tested each one for resistance and each was around 0 or no resistance. I just ordered a replacement ev1 board as there is some corrosion on mine. I figure it is worth the $100 to just be sure that is not the issue.
  • Posted 28 Aug 2012 07:20
  • Reply by specequip
  • Michigan, United States
you do have cables that run under/beside the battery to the drive motors from the controller and contactor panel in the back.
Thanks for correcting me about the short being only on the battery meg cable to the case of the battery, my misunderstanding of what was said.
as this is a 2 motor system, there should be 4 directional contactors, right and left pairs of forward and reverse, and they should pull in, as pairs, if the rear wheel is in the straight ahead position.
  • Posted 28 Aug 2012 07:15
  • Reply by edward_t
  • South Carolina, United States
"it's not rocket surgery"
Just jacked the front wheels up and reverse is working as is forward. I noticed some sparks on the front forward contactor. It seems that the front 2 are wired together with a bar. I also noticed that it only mpt's going forward with the wheels jacked up.
  • Posted 28 Aug 2012 05:00
  • Reply by specequip
  • Michigan, United States
That short was from the battery negitive terminal to chasis. I cannot find another short. With the battery removed I have no continuity to anything. There are no power cables under the battery only hydraulic lines. With the battery out of truck we can replicate the PMT and now have no reverse. I am not sure what to do next.
  • Posted 28 Aug 2012 00:07
  • Reply by specequip
  • Michigan, United States
you -DO- have a short. and you found part of it when you found "negitive terminal to chassis show about 83.6 ohms", now trace where that 83 ohm short is coming from, then your problem may well go away.
You found -part- because it is a circuit, and you have only found part of the complete circuit. now disconnect the other end of the cable from the heat sink or if it has an insulated standoff and check each of the wires connected there. for ohms to frame. be sure to check the heat sink too, as it has a Mylar sheet insulation under it and has little plastic insulators for the mounting bolts that can cause this sort of short (you may only be chasing a wet wad of dirt, for all we know at this stage, the ohm meter will tell us where it is).
Reading -voltage- to frame has no value other than to tell what cell in the battery is the 'most shorted', your meter does not draw enough current to tell if the current being measured could have enough flow to do anything other than be measured as a 'potential', and even a 6 week old battery will show some voltage to frame, but not much OHMs.
All the cables under the battery, that are covered in white, will need to be replaced or at the very least cleaned and ohm checked. I would replace them all if you are going to keep this truck at least 1 year more, as you will have weird intermittent failures (a.k.a. 'wifs') due to the corrosion saturation of the insulation of these cables. clean out all the corrosion under the battery compartment and check for nicks and cuts where the cables touch the battery box sides and frame of truck
83.6ohms is much less ohms (more shorted) than the minimum of 100,000 ohms I (and GE) said you needed to check for.
Disconnect the cables (that you are reading less than 100k ohms) from every other connection. and check that cable again, and all the other cables it was connected to. Trace the short to it's connection to the frame.
  • Posted 27 Aug 2012 01:39
  • Modified 27 Aug 2012 06:54 by poster
  • Reply by edward_t
  • South Carolina, United States
"it's not rocket surgery"
Pulled out the battery today. Tons of white buildup. Hooked it up and it is the same. I was sure hoping for a short. or something easy to fix. We are going to try to equalize the battery and go from there.
  • Posted 25 Aug 2012 06:04
  • Reply by specequip
  • Michigan, United States
You getting anywhere with this? Will it jump and shut down at 1/2 throttle? I had two service calls this week, one with a EV1 doing what yours does and one with a old EV100 with a slightly different problem. If you need further help e mail me and I will send you a list of things to check to try to help you figure out what's wrong.
  • Posted 24 Aug 2012 20:52
  • Reply by mrfixit
  • New York, United States

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