Any JLG boom lift gurus here?

motion guru · Aug 19, 2017

I bought an older JLG boom lift and went through it mechanically and got it running really well. It is a 1999 model but the motor data plate says 2007 and the hour meter has 3200 hours.

The "Creep" speed setting doesn't work for the boom rotate . . . as in, it doesn't rotate at all. It rotates fine at the normal speed but when you are 40 feet up in the air next to a window it's kinda nice to take it slow and easy.

The wheel speed and raise/lower each work at nice controllable reduced speed when I turn the creep speed switch on, but the boom rotate stops working all together. Where do I start looking to fix this?

ratbldr427 · Aug 19, 2017

Hard to tell,but since it is used maybe someone did some rewireing.I don't think they are supposed to rotate in fast mode when elevated?

I think we have a rental JLG in the plant now.If so I will check Monday and see if there is a schematic with it.Although it most likely a lot newer model.

Fabworks · Aug 19, 2017

I did a bunch of work from a JLG folding boom several years ago. As I remember it had some kind of internal tilt meter that would cause it to move slower when it was past a certain point of out of level. :confused:

motion guru · Aug 20, 2017

This has the tilt circuit and it works as it should. I have been searching the internet for a manual and came across a 152 page PDF that has wiring diagrams with motor controls, hydraulics, safety circuits all described by wire color and number, but none of the devices that they are wired to are identified by anything other than terminal number.

I can physically see a couple of Mico brakes and proportional valves but all the wiring has been painted over obscuring colors and labels so figuring out the actual schematic has been a pain. I might need to stop by a place that rents them and see if they have access to a better manual.

DDoug · Aug 20, 2017

Is the 2 speed swing accomplished by a double gear motor ?

Travel on the mini excavators is done this way.

Slow speed, the oil goes thru both sections in parallel,
fast is a solenoid shut off 1 section, same amount of
oil going thru 1/2 as much gear section.

Or is the 2 speeds from just a solenoid and a speed control
(restriction valve)...could be the solenoid is bad, or plugged.

motion guru · Aug 20, 2017

digger doug said:
Is the 2 speed swing accomplished by a double gear motor ?

Travel on the mini excavators is done this way.

Slow speed, the oil goes thru both sections in parallel,
fast is a solenoid shut off 1 section, same amount of
oil going thru 1/2 as much gear section.

Or is the 2 speeds from just a solenoid and a speed control
(restriction valve)...could be the solenoid is bad, or plugged.

The motor has only two ports. The "Creep" switch affects 3 functions:

1.) Wheel Drive
2.) Boom Raise / Lower
3.) Boom Rotate

All function normally when not in creep mode.

The Boom rotate doesn't function in creep mode however, I can hear the engine load up ever so slightly when operating the control, I wonder if the brake isn't releasing in slow speed or the checked return valves aren't seeing enough pressure to release?

I need to figure out if the creep speed switch is putting some kind of voltage divider in the control circuit or cutting the hydraulic flow rate to the proportional valves for these three circuits.

There are two bang/bang solenoid valves (steering cylinder and boom extend / retract) . . . neither of these are affected by the creep switch but both of these valves are in the same manifold stack as the proportional valves. I really wish I could find a schematic.

It is a 1999 JLG 40H unit

On edit . . . the heavy equip version of PM has some good info - JLG 4h lift, swing, move all stopped working suddenly | Heavy Equipment Forums

petersen · Aug 20, 2017

Not a GURU, just an owner/operator with a 2001 mod. 600S.

That rabbits and snails selector (potentiometer) acts quite differently on

different machine functions.

On mine the basket rotate and tilt functions do not operate on or near creep speed,

but are quick when you turn that pot. up a ways. The main swing and boom hoist are

only a little slower at creep setting (perhaps half) then at wide open.

I had to go out and look to see that mine has been at max for a long time,

and my joy stick control is sensitive enough to easily move a fraction of an inch

out at or near full extension .

A tip for fine movements out at the end of that long whippy boom;

keep an eye on the house, counterweight, and background, and you can see the first

slight motion well before you will feel it out on the end of that boom.

But then you're the guru...

petersen

motion guru · Aug 20, 2017

Yes, I have found a lot of differences between models. On the 40H the only items that change speed are the 3 listed above. Basket rotate and level as well as steering and boom extend/retract are all plain old solenoid valves with full speed all the time.

I posted the question on the heavy equipment forum and will see if someone can point me in the right direction. I have been pressure washing my house and bracing myself to rotate is unnerving 40 feet in the air (and I have only hit a volleyball net post so far) no damage . . . although I have also learned to raise the basket a few feet so you don't drag it on stuff when driving over sidewalks.

petersen · Aug 20, 2017

The service manual for our 60S has about 20 pages of electrical and hydraulic

schematics for different engine and equipment combos.

They do typically show the rabbit/snail switch next to a flow control card

and three other cards marked main lift, swing, and steer.

If you have no luck finding the right diagrams for your 40H, contact us and

I will have one of our younger generation scan these for you.

petersen

DDoug · Aug 20, 2017

motion guru said:
Yes, I have found a lot of differences between models. On the 40H the only items that change speed are the 3 listed above. Basket rotate and level as well as steering and boom extend/retract are all plain old solenoid valves with full speed all the time.

I posted the question on the heavy equipment forum and will see if someone can point me in the right direction. I have been pressure washing my house and bracing myself to rotate is unnerving 40 feet in the air (and I have only hit a volleyball net post so far) no damage . . . although I have also learned to raise the basket a few feet so you don't drag it on stuff when driving over sidewalks.

I thought you posted (or someone else did) that the creep/fast
on the swing was different in that it was selected automatically by how far the boom was extended, not a manual switch on a panel.

Any swing I have been around, excavator, mini excavator, etc,
all have a brake, run off the same 2 hydraulic lines, plumbed from the valve, to send the motor either CW or CCW.

JHOLLAND1 · Aug 20, 2017

spent past 2 days getting my 60 ft simon/RO manlift back in service

very different electrical than JLG

but--my unit--mid 80's--had two non-contact wires hidden by crimp spade connectors--I pulled many plug unions apart and stripped/wire nuted questionable connections--this fixed the problem

I share same weather locale as Mo Gu

Helligso · Apr 10, 2019

This is an old thread. Is anyone still following it? I have a JLG 40H that the steering and travel are not working on.

motion guru · Apr 12, 2019

I ended up replacing the joystick controls with new versions. The creep speeds are determined by pot settings on the joysticks. I bought aftermarket units off eBay that are far more moisture proof than the originals.

This would affect travel, but steering on my unit is controlled with a solenoid valve and not a proportional valve like the travel. Check the link in my earlier post for the heavy equipment forum that has regular posts on this model.

tmt · Apr 12, 2019

Helligso said:
This is an old thread. Is anyone still following it? I have a JLG 40H that the steering and travel are not working on.

Yep a little old.

I don't have a JLG boom lift, I have a Genie boom lift around the same vintage. Although they are not the same Mfg there concepts are similar and some parts are the same.

It probably is something simple.

Check the level sensor on the main unit. If it is malfunctioning, it won't move, Check all the relays contained in the control boxes, main and lift bucket. They normally are the automotive style little cube type with 5 blade prongs. Cheap and readily available. Also check all the fuses and breakers as well as connections and wiring. Since neither travel and steering are working, it must be something in common with both. This is where a wiring schematic comes in handy as well as a hydraulic schematic. There are some control boards boards, main and lift bucket panels that provide routing of the control functions and without a good service manual they may be difficult to trouble shoot.

Good Luck!

tmt · Apr 12, 2019

motion guru said:
I ended up replacing the joystick controls with new versions. The creep speeds are determined by pot settings on the joysticks. I bought aftermarket units off eBay that are far more moisture proof than the originals.

This is the first I have seen this thread and after reading your problem description my first thought was the Joy stick control boards. My swing control was stuck in slow mode which didn't bother me too much since I am retired and use it for trimming my trees. I tried everything by the book on adjusting the trims with no avail. This past summer I had to get a boom hydraulic cylinder rebuilt and decided I had the time to go through and fix all the little things that bugged me I broke down and bought the swing control boards and after installing them I remembered how nice it was to have the proportional speed back to normal. Of course I bang into the limbs a little more often that I use to!

Glad you got yours fixed.

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