JLG 40HA travel speed problems

[mudhole4x4]

I have a 40HA and I was having problems with my brakes randomly locking up. I think I have fixed that finding a bad relay in the main control box and also maybe a bad ground at the solenoid. Now I have a problem with my ground speed. What’s happening is when you are traveling in any direction in LOW ENGINE speed and LOW TRAVEL speed the machine will sometimes speed up and won’t creep or go slow. I checked the voltage leaving the joystick in the platform, down at the main control box and when low speed is selected I have from 0-1.5 VDC coming in the term strip. When high is selected I have 1.5-3.5 VDC at the term strip. It’s not doing it all the time just for a few seconds every few minutes. Any thoughts on what I could check and I was also wondering how should the dump relay and valve work? Mine when you press the pedal in the platform will energize the dump valve what is that supposed to be doing? Thanks for any help

 

[willie59]

What type of controls do you have at the platform?

1) Bang-bang controls; toggle switches for boom functions and a single P/Q proportional controller for drive.

2) Electric proportional P/Q controls for main boom functions and drive mixed with toggle switches for other functions.

Or 3) hydraulic control valves with a single P/Q controller for drive.

 

[mudhole4x4]

ATCO thanks so much for your help friday afternoon the manuals i printed out helped me alot......... i have the hydraulics in the basket. Do the foward and reverse wires go to some sort of hyd. fluid control valve?

 

[willie59]

No problem.
Listening to you on the phone yesterday...you don't sound like your originally from North Carolina.

The boom and steer operations work by a 2 stage gear pump. One pump delivers oil to the lower control valves. The other pump goes through the dump valve, then to the platform control valves. The purpose of the dump valve is to disable the upper controls by dumping oil back to tank when your not operating the machine so you can't accidently jab something into a control lever and make the machine move. When you step on the footswitch, the dump valve delivers oil to the upper controls so you can operate machine functions.

The drive works from a bi-directional variable piston pump that has an internal charge pump. The charge pump delivers oil to the piston pump and to the brake control solenoid valve. The output of the piston pump is controlled by a servo on the side of the pump that recieves voltage inputs from the proportional P/Q controller at the platform controls. When the machine is not driving, the servo holds the swash plate of the pump in the null position, not moving any oil out of the ports. When you move the control lever at the platform, it sends a voltage signal to the servo to move the swash plate and produce output out of the port for either foward or reverse drive. As for your drive speed (creep), when you select creep you send a voltage signal to pin #7 on the P/Q controller, and the controller now reduces the voltage output to the servo on the pump. Your erratic drive problem could be caused by a number of things, but one would be the drive controller. Those P/Q controllers are tricky to adjust, they're actually adjusted with an oscilloscope. Does your controller have adjustment pots labeled Hi Range, Lo Range, Threshold, and Ramp?

 

[mudhole4x4]

i dont think so, its an epoxy filled board.... i have a enigine high speed and low speed toggle and a drive high and low toggle...i see what i assume to be the correct voltage when i move the joystick and when i toggle the drive high and low at the bottom control unit.... i went out there a second ago and when i step on the pedal it now cuts off i think i have another relay sticking. thanks for your help

 

[willie59]

If you don't have any adjustment pots on the controller circuit board, then everything is preset. The drive problem can be caused by a faulty servo at the pump (although I haven't seen that happen often), problem with the cable from lower controls to upper controls, or a problem with the controller. You might want to consider sending the controller and having it tested for proper operation. I send controllers to Hindley Electronics in Ohio.

http://www.hindleyelectronics.com/index_option.htm

Give them a call and they'll tell you what's involved in having your controller tested.

 

[mudhole4x4]

thanks i will give them a call.....i am going to troubleshoot the pedal cutting the machine off tommorrow afternoon

 

[willie59]

...i am going to troubleshoot the pedal cutting the machine off tommorrow afternoon

Huh?

You mean the engine dies when you depress the foot pedal?

 

[mudhole4x4]

yes, i have to look and see if the dump relay is tied in with the ignition relays somehow, but yeah it just started doing that today, i know the dump relay is sticking so i have some weird troubleshooting to do, i had 5 relays laying around i think i am going just to save time start swapping some out

 

[willie59]

Sounds like you have some kind of electrical problem that could be the root of all your problems. The dump valve circuit has no connection to the ingnition circuit directly, but the dump relay is powered by the same circuit that powers the ignition relay, terminals 35 thru 39 on the lower box terminal strip. You need to do some voltage tests. Connect a voltmeter to the red wire on the circuit breaker in the lower control box, that's your positive feed from battery. Press foot switch and see if voltage drops. Connect meter also to the screws in terimals 35 thru 39, those are terminals that distribute power to the various operations, see if the voltage drops there when operating machine.

 

[mudhole4x4]

yeah, i am going to check those things tomorrow afternoon. thanks for your help....:drinkup

 

[mudhole4x4]

When I push the pedal I don’t loose any voltage at the ground controls circuit breaker or the power distribution at the term strip. One thing I did notice is the ignition solenoid would close and stick sometimes it would release like it was supposed to and others not. I changed out the ignition solenoid and the problem went away. I tried the pedal with it running probably 20 times and no problems after I changed that relay. I changed the dump relay as well due to it not working right from the day before. I then drove it around the yard for about 20 minutes or so selecting high engine and low engine also selecting high ground travel and low ground travel and had no problems so I am sure as soon as I go to actually use it, it will mess up again but for now all is good. I almost forgot when I changed the ignition relay and looked inside I think it has been mechanically latching to ground and maybe that was intermittently switching some of the other relays. Not sure, it will be the end of the upcoming week before I can start back to work with it. Thanks so much for all your help ATCO and I will post later after I have used it a little.

 

[willie59]

I am sure as soon as I go to actually use it, it will mess up again

Hmmm, well at least ya got confidence goin' for ya'.

For the heck of it, check one more thing. Check the ground cable from the battery where it connects to frame. I have seen that connection get corroded or rusted and during cranking the starter would draw enough amps to make an arc to enable current flow for starting, but once started, the corrosion would cause problems for lighter currents required to operate the machine. Nothing lost in taking a look at it.

BTW: Where's my manners...welcome to the forum. :usa

 

[mudhole4x4]

i have drove it around every afternoon for the last few days for about 20mins or so and so far everything seems to be ok.......

 

[mudhole4x4]

Well I think I have identified the real problem I was having…. When it rains I think the PQ E120 was getting crazy. Just after the rain this morning my lift started acting up. I should have like 0-1.5 VDC at low and 1.5-3 at high I think but now I have 9VDC at any position and at any level of speed. The PQ is also not outputting the voltage to energize my brake solenoid so that would explain my lift locking up and putting the motor in a bind. I put a hair dryer on the controller with no luck. It is even now driving when you press the pedal with no joystick movement. I hate to spend so much money on it being as I am borrowing it from a friend but I guess I have to get it back running dependable. I think I have a PQ E120-B13 controller. Anyone have a cheap one lying around or knows where I wouldn’t have to spend a fortune to get one?

 

[willie59]

It is even now driving when you press the pedal with no joystick movement.

I'm not sure which model PQ you have, did you try disconnecting the wires from the A and B terimals of the controller, or disconnect the plug connection if you have a harness connector, then see if it tries to drive with footswitch depressed? I haven't purchased one for a while, but I'm thinking you can you can get a rebuilt circuit card from Hindley for like 70 to 100 bucks.

 

[mudhole4x4]

PQ E120-813 PQ part number 7003783.... Yeah if you unplug it, it doesn’t do anything its not supposed to. I jumped out the brake circuit at the basket because my controller stopped outputting @ the 5 degree like it’s supposed to and the unit moved fine just at the wrong speed and sometimes in the wrong direction. I checked I have found a new one for $255 from Hindley or I could send mine in to have rebuilt for like $140….. I am still looking to see what I can find.

 

[willie59]

PQ E120-813 PQ part number 7003783.... Yeah if you unplug it, it doesn’t do anything its not supposed to. I jumped out the brake circuit at the basket because my controller stopped outputting @ the 5 degree like it’s supposed to and the unit moved fine just at the wrong speed and sometimes in the wrong direction. I checked I have found a new one for $255 from Hindley or I could send mine in to have rebuilt for like $140….. I am still looking to see what I can find.

That's about right. To have yours rebuilt would be $140, that includes handle rebuild. But if the mechanical components of your controller are still in good shape, all you need is a new circuit card. I'm thinking that's less than 100 bucks.

 

[mudhole4x4]

Something still isn’t right..... but I ordered a new controller so at worst case i would have to send it back and be out the restocking fee.....I have my 12VDC coming out of pin 2 (which is my brake solenoid) but my brakes wouldn’t release yesterday so I wonder if my controller is opening up under the relay load.... I will have to check that today but my new one will be here Thursday. I still believe it’s the controller with different results every day it seems like.

 

[willie59]

Yep, I've seen that before. In most cases a controller will crap out and just won't operate properly, not so hard to find them. But I have seen the occasional controller that can't make it's mind up. That's where it's nice to be working on a JLG that has several proportional controllers, you just switch out with another that is working properly and see if current problem goes away or moves to the function you switched with. That's the only bummer with you having hyd controls and a single electric controller for drive. Keep us posted.