Crown RC3000:
Help! - No forward travel!

Hi all,

I work at a company and we have a Crown Forklift, RC3000 series, model 1A225187. It's a three-wheeler standing forklift. It currently has no forward travel, only back. If I go backward, it goes fine. If I try go forward, it clicks repeatedly near the foot pedal and will sometimes jolt forward an inch or so. I've tried dusting out the connections - apparently a former employee at my work made it work again like that.

Unfortunately, I haven't been able to! Any advice on how to fix this would be greatly appreciated!

Thanks,
Petar
  • Posted 31 May 2017 14:01
  • Modified 1 Jun 2017 06:49 by poster
  • Discussion started by Petar
  • Wellington, New Zealand
Showing items 1 - 14 of 14 results.
Wow, so I had no idea what was going on...

So if you look at the ev100zx manual, we'd be at least talking about the same page numbers, which is drawing on page 5 and explanation on page 15.

The control circuit is energized by closing the key switch, seat switch, and moving the forward
or reverse lever to either position, and then depressing the accelerator closing the start switch. This
applies power to the control card turning on the PMT driver , which will close the selected directional
contactor and complete the circuits to the drive motor. (See elementary drawings.)
The control card then supplies a gate pulse to 2REC turning it on to a conducting state, allowing
current to flow from the battery through lC, lX, 2REC, motor field, motor armature, sensor, and
back to the battery. After lC charges, 2REC shuts off due to lack of holding current. The control card
checks that lC is charged and unlocks the gate to lREC and 5REC.
The control card then supplies a gate pulse to lREC turning it on to a conducting state, allowing
current to flow from the battery through lREC, motor field, motor armature, sensor, and back to the
battery. 5REC turns on and allows current to flow T4-T3, lC, lREC, 5REC to T4-T3. This current
charges the bottom of lC positive with respect to the battery positive bus. This charging cycle occurs
in less than l millisecond (.00l sec.) and 5REC shuts off. This charge is now stored on the capacitor
until it is time to turn off lREC.
Current continues to flow in lREC until the control card fires 2REC. When 2REC conducts,
capacitor lC discharges around the circuit composed of lC, 1X, 2REC, and lREC. This discharge
current opposes the battery current through lREC so that the resultant current is zero. With reverse
voltage across lREC, lREC is turned off. Current continues to flow in the 2REC, lC, motor and battery
loop until the capacitor (card terminal l4) is fully charged negative. This charge exceeds battery
voltage by an amount which is a function of peak motor current, and 2REC turns off. Figure l illustrates
the pulsing of current from the battery.

What a.....

Ok so maybe my explanation will be easier to understand, maybe not. When you start going forward, the current that goes to the motor is only the current created by charge leaving the cathode of the capacitor while charge enters the anode of the capacitor thus lending a positive charge to the capacitor. This current flows though 2rec, and the directional contactor and the motor, when the capacitor is charged so that it's anode, relative to it's cathode, is at full battery volts, electrons will no longer flow. because they do not flow, there is no current across 2rec. 2 rec by nature of insufficient current self opens as all thyristors do when charge stops flowing. Now the control card can tell that the cap is charged, so it triggers the gate on 1rec, and 5rec. 1 rec supplies current to the motor and 5rec, which allows current to pass through to the capacitor, which means the capacitor has equal emf acting on it, and so it wants to equalize voltage potential across it's anode and cathode, so it's going to get balanced, with charge on both sides. When this is equal, no more current can flow, and 5rec shuts itself down, thus keeping the cap charged, isolated and ready to do something very important. When you stop moving the stick forward, the truck is supposed to open that contactor, but doing so while current flows would be bad for the contactor and the motor and would create a huge spike of something across the whole electrical system that would be rough on the whole unit. So the card uses a gate pulse to activate 2rec, and that allows the cap to equalize voltage on both sides of 1rec at the same time, so that 1rec shuts itself down as no current is flowing and thyristors only stay open when there is sufficienty current...

..... I still don't know where the....half battery voltage comes from. Hahahaha.

I'm wondering if it has to do with full voltage on one side of the cap, half voltage on the other side, and then another circuit element maybe even another cap somewhere, which when not in use represents a circuit at equilibrium with no current passing through the card, just a chain of decreasing voltage across a series circuit..

Maybe its coming form the card somehow, as part of a speed control feature which is activated in error, or something like that.

I definitely need a handset. Why are these things so obscenely expensive?

Maybe I can simplify this enough that its close to the thing you tried to tell me.

The 2rec provides a slow current ramp, to prevent jolting and sparks, and a current neutralizer to shut off 1rec, and the 5rec regulates the recharging of the 2rec device. Without 5rec, 2rec would be spent after turning 1rec on and 2rec wouldn't be able to turn 1rec off nice and clean.

My traction potentiometer at least is reading the specs it seems like it should.

I gotta track down this half bat volt thing, and see if I'm leaking charge somewhere when I shouldn't be, or what's happening.

The warehouse guys had installed a bunch of extra read outs, locators, scanners etc, to the truck when it was running potato chips, and it might be that one of those wires they hacked off is connected to something that's grounding out or providing charge where it shouldnt...

I really appreciate you trying to help. I'll get this thing figured eventually!

and ummm to answer your question... I'm just unreasonably curious. My dad was a fancy scientist... so I'm sure I picked up some of the tendencies from him... but I'm just a hillbilly trying to stack.... in my barn, so I can organize all the pumps and motors and hydraulics and electronics...

I guess I'm kinda trying to teach myself to be an electric engineering designer, cause I want to..... around with autonomous farm robots, but I just read a lot, and I'm stubborn about dropping things I don't understand, so I just keep reading...and watching videos and looking up explanations on forums and MIT coursework and discussions between professional electricians or whatever... I have to until I convince myself I know what I'm talking about... but sometimes I have no... idea, which I got to find out tonight. That was fun, I think I actually have half a clue now, and uhh, couldn't have done it without you. Srsly though i've been trying to get this for 2 weeks, and for some reason you really helped me actually get it, even if you feel like you didn't do much, you should feel proud or something. Thanks for lending a hand.
  • Posted 22 Nov 2019 13:51
  • Modified 22 Nov 2019 22:43 by administrator
  • Reply by Pastoral
  • Washington, United States
allen.markeric@gmail.com
WOW, are you some kind of program developer? I have no idea what you are saying. But, in my 25+ yrs experience working on these systems, it's better to keep it simple. The 2rec turns the 1rec gate "on", and the 5rec turns it "off"....really really fast. You need your inputs to the control card, brake and deadman switches under the floorboards, fwd or rev switch input. And lastly, the traction potentiometer. These inputs are on the 6 screws on top of the control card. The potentiometer input should be 3.5 -3.7 volts neutral, and as you slowly request travel, the value drops to near zero. Let's get back to the original question, no forward and reverse works. Start with the fwd switch. Resistance through those switches should not be more than 0.5 ohm. Once the control card see's the brake/deadman/and travel switch, it supplies a negative to the traction contactor, either fwd or rev.
  • Posted 22 Nov 2019 12:45
  • Modified 22 Nov 2019 19:27 by poster
  • Reply by Ifixit
  • Pennsylvania, United States
Hey, thanks for getting back to me. I will try that arrangement and tell you what I read.

The thing is, I disassembled all inputs to the 1rec, to test it, as per the suggestion in the EV100 tech manual posted on FSIP. It told me to use a 6volt supply, energize the anode, negative on the cathode, got full ohms, like 30 megs or something, then jump the postive to the gate, thryristor opens, latches, stays open.

Like it's doing exactly that it's supposed to do when it's entirely isolated from the circuit. It's using the resistor capacitor combo of 22 rec and 25 rec coupled to 2rec and 5rec driven somehow by the leads coming out of the logic oscilator board which connect to various parts of those assemblies to control the voltage output going through 1 rec,

I'll be honest, I don't know how it works exactly... I'm not sure if I'm dumb, or if I don't have enough documentation yet to understand the circuit. I mean... I know me being dumb is a part of it, but I'm hoping there's other parts too.

An SRC in isolation without any input is just going to remain closed when you energize the anode with 36-40 volts (well this SRC is cause it's breakover voltage is way higher)

Somehow the logic card and the other SRCs/thyristors (same thing, just bell/ge name vs standard name) are limiting turning off the 1rec thyristor when the t2 (which is the 1 rec cathode) voltage is up to 1/2 the 1 rec anode, which is bat pos, and something in that assembly on this card isn't right, because it's cutting off the thyristor way **** early and it's killing the contact when it's up to only 3.6 volts. Replacing the 1rec wont solve that, because the 1rec is already operating according to the GE tech manual expectation in a 6 volt gate activation test.

as per the GE manual:
well apparently I can't copy and paste, but like functions 11-13 are speed limit inputs. I'm guessing this is something that would be engaged in a few scenarios. One that I'm aware of is when you have an elevated mast value read by the controller, and it limits speed depending on your steering. right? So it does this by having 255 steps, cause it's running an 8 bit binary control machine code i guess, and it's running 256 values, 2^8, and it's starting at 0, ramping up to 255. at.375 volts per step, and it won't let the volts go higher, or it subtracts that voltage from battery, I'm not exactly sure. But it's basically limiting me 10 steps above stopped, if that's the mechanism at play that is preventing me from whatever whatever. It could be something else. but yeah, that's what's going on.

When the guys at the warehouse loaded it, they basically said that they couldn't creep with it, but they knew how to jump it into full battery voltage contact to the motors, so they could load it onto the trailer, but if I can determine what is artificially limiting the voltage output from 1rec, I should be able to get the correct voltage at the t2. Do you think I should just try unplugging leads related to voltage regulation one at a time, and see which one when removed stops preventing regular operation of the 1 rec?
  • Posted 22 Nov 2019 12:01
  • Reply by Pastoral
  • Washington, United States
How did you measure T2? To check the 1rec, unplug the battery, remove the 3rec pigtail and power cable from the left side and keep them from touching anything. Plug in the battery, battery volts will be on the right side of the 1rec...and half battery volts on the left. Any other reading (higher or lower) than EXACTLY half battery volts, the 1rec is bad.
  • Posted 22 Nov 2019 11:28
  • Reply by Ifixit
  • Pennsylvania, United States
Hey bud, hoping you could verify if this sounds like a good reading or indicative of a problem. I'm not getting half bat at T2, on the main SCR, which I think is causing a failure to actuate contacts for the drive unit, So I wanted to see what was the cause. I stripped down the SCR, applied 5.9 v to the anode, and the meter pos, and the negative of the 5.9 battery voltage to the cathode along with the meter. Voltage difference was 5.9. Then I jumped the anode to the gate, and the SCR closed, conducting from anode to cathode, but there was enough resistance in it that I saw a 1.2 V difference between the anode and cathode.

Since the circuit at that point is literally bat pos, anode, cathode, bat neg, it makes sense to me that the SCR would represent significant R value for the total circuit and constitute a voltage drop of that value, but I'm smart enough to not rely on my intuition yet. The gate control caused the SCR to latch, and I maintained the volts after removing the jumper, restarted conduction instantly each time. Seems like a good SCR to me, but maybe I'm missing something? Open Ohms was something like 20-30 mega ohms and then the voltage from the multi meter somehow modified it, and it jumped up to infinite (as far as my Fluke 117 can manage to see)

I think anode to gate might have been teens or 20 ohms.

Does that all sound like a solid SCR, or am I totally missing something?
  • Posted 14 Nov 2019 12:04
  • Reply by Pastoral
  • Washington, United States
Alright, I might as well create an account over there, I'll need to buy something sooner or later. Thanks for the tip, I might have just avoided OEM assuming it would be unreasonably pricey.
  • Posted 14 Nov 2019 03:16
  • Reply by Pastoral
  • Washington, United States
Order one at Crown dot com or on Ebay. All Crown manuals have both parts and maintenance in the same book.
  • Posted 14 Nov 2019 01:56
  • Modified 14 Nov 2019 01:57 by poster
  • Reply by 1Crusader
  • California, United States
I didn't do it, nobody saw me and You can't prove a thing...
Not a bad suggestion. Another guy mentioned it to someone else so I asked him how I said go about finding one, haven't heard back yet though, would you just turn to eBay? Right now they seem super pricey.
  • Posted 13 Nov 2019 16:24
  • Reply by Pastoral
  • Washington, United States
You really only need a handset if you are changing the control card. If I were you I would spend the money on a shop manual so you could look up parts and compare prices.
  • Posted 13 Nov 2019 07:46
  • Reply by 1Crusader
  • California, United States
I didn't do it, nobody saw me and You can't prove a thing...
Hmm,

Well I'm just fixing up a rig for my home shop, so I'm willing to save some money, but ultimately I want it to work. Do you think it's worth buying a handset? Would you eBay that considering my personal use case? Is there a go to site that is trustworthy and cheaper than crown? How do you feel about the fsip.biz?
  • Posted 13 Nov 2019 02:59
  • Reply by Pastoral
  • Washington, United States
Well, when I work for Crown I used Crown parts. You can use parts from other sources but be careful to make sure they are the same, like amp. rating and such.
  • Posted 13 Nov 2019 01:51
  • Reply by 1Crusader
  • California, United States
I didn't do it, nobody saw me and You can't prove a thing...
What's the go to location for parts in your opinion?
  • Posted 12 Nov 2019 18:03
  • Reply by Pastoral
  • Washington, United States
Whenever this condition happens at one of my customers, I replace ALL the switches in the system. 2 switches under the pedals, and both travel switches. They are cheap and the customer won't be calling back for a "same condition " complaint breakdown call.
  • Posted 20 Jun 2017 07:50
  • Reply by Ifixit
  • Pennsylvania, United States
If you have no forward travel when reverse works fine, I would look first to see if you have contactor pick up in forward travel. If not I would be looking at the forward switch. if you do have contactor pick up then I would be looking at the directional contactor tips. Check forward switch and don't forget you have other travel interlock switches under the foot pedals.
  • Posted 9 Jun 2017 06:55
  • Reply by 1Crusader
  • California, United States
I didn't do it, nobody saw me and You can't prove a thing...

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