JLG 40h lift, swing, move all stopped working suddenly

[brad40h]

The lift up/down swing left/right and move forward/reverse all stopped working together. Stepping on the foot peddle still causes engine rpms to increase. I did check for 12 volts under the basket control console, its present with foot peddle depressed. I suspect I have hydrualic pressure as the boom still telescopes in/out ( but this is on a seperate valve block from the lift/swing/move valve block). I have the PQ controls. When I actuate the lift or swing PQ joystick, the engine does not change rpm, ie engine does not see a load. When I actuate the move PQ joysitck, I get a very slight change in engine rpm. If all three functions stop working together, what could be the causes?

Thanks

 

[willie59]

Welcome to brad40h. :drinkup

It sounds like the proportional dump valve is either not working or is not getting power. You need to check if relay R16 has power on the orange/red wire going to relay terminal 86, check if yellow wire going to relay terminal 30 has power, and see if power is leaving relay on terminal 87. If all that's working proper check the proportional dump valve operation.

 

[brad40h]

Willie59

Thanks for the help. I traced through the circuits as suggested and everything works as expected. I then noticed that the creep mode switch was enabled by mistake. I disabled creep mode and the lift works as before. I don't understand the theory of operation behind the creep mode by looking through the wiring diagrams. I would like to fix the creep mode operation so it is usable. When creep mode is enabled, the proportional dump valve is open as I have checked this. Any thoughts on what else to look for?

Also, the automatic choke gives us fits when the motor is warmed up. It wants to flood the carb. No amount of adjustment has fixed the issue. Other than a jlg dealer, where can one find parts (Ford motor in this lift) online?

I have read through your past post's and have learned a lot the last couple of days: much appreciated.

 

[willie59]

It sounds like you need to adjust your controllers. When the creep is adjusted properly on the controllers it reduces the output from controllers to the proportional valves. The purpose is when you have the boom extended, and you select creep mode, the proportional functions operate slowly, which is ideal when working close to objects with the platform.

If it has a Ford engine it most likely has a Zenith carb. Have you checked that you have power going to the heater for the choke bi-metal spring? Have you verified heater is working? Have you verified the bi-metal spring is not broken or not attached properly? Is the choke plate shaft free to turn?

Check the Zenith website for a distributor. > http://www.zenithfuelsystems.com/

 

[excavator]

I've been working on a 40H, put a new ring gear & starter in it. Was working on it yesterday fixing several other things when the boom lift and swing quit working at the end of the day,travel still worked. So this morning I drove it about 75 feet to get it into the sun and the travel quit working. I'm getting no power to the prop. dump valve. If I hot wire the valve all 3 prop. functions work. At the prop. dump relay, R16 I've got power on yellow wire to term. 30 and ground on term. 85 but no power on orange/red to term. 86 so therefore nothing on orange/red term. 87 to the dump valve. Where does the power to term 86 come from? From what I can see the wire goes to term. 9 on R2 lift relay but this relay seems to only be powered up when the selector switch is in ground control position. What am I missing? Hopefully Willie or Off will see this tonight and enlighten me abit. Thanks in advance!

 

[willie59]

Standard control machine with Ford engine?

 

[willie59]

Ok, assuming we're working with a standard control machine with Ford engine, you are correct, the orn/red at proportional dump relay gets power from terminal 9 of R2 select relay. The R2 select relay prevents both platform and ground controls working at the same time. It's a 3 pole relay, A and B operate the relay coil, terminals 7 8 and 9 are common terminals, terminals 1 2 and 3 are NC, terminals 4 5 and 6 are NO. Here's a diagram of a 2 pole relay that works the same way, just missing the third pole circuit of 2 5 and 8.







And you are correct again, the only time the R2 relay powers up is when you select "ground controls", this powers up the relay, disconnects the platform controls from the circuit at terminal 3, and allows the ground controls to connect to the dump valve via terminal 6 connecting to terminal 9, the NO circuit is now closed.

When you select "platform controls", R2 coil is dead, now terminal 3 is connected to terminal 9, the NC circuit. Power comes to terminal 3 from the orn/red wire of the 16/30 cable from the platform. Orn/red wire is connected to terminal #14 at the platform box terminal strip, terminal 14 gets power from terminal 35 when foot switch at platform is depressed.

 

[excavator]

Thanks so much Willie. This helps a lot, I'll check it out in the morning and let you know what I find. This forum, thanks to you and many others has more information in it than most JLG manuals. I actually print these posts out and put them in the manual for further reference. Thanks again.

 

[willie59]

No problem, glad I could help. In all honesty, JLG diagrams aren't the easiest to read, I just have a bunch of years of experience with them so it's just a tad easier for me. Also, I've found errors in JLG diagrams, that will really make you scratch your head trying to figure something out. :Banghead

 

[excavator]

Yes, I'm finding that experience is much more valuable in lifts than having the manual. I've been a mechanic for 35 years, heavy equipment the last 20 and have just started doing lifts the last couple years and I've scratched my head many times. And I've never seen any other machine that former mechanics have cut and spliced and added as many things as on these lifts. Some could also be updates that never made the manual?

 

[willie59]

Well, the more you work on them the more you get familiar with the common methods in aerial lift designs. And when it comes to working on them, especially the electrical, those older JLG's are hard to beat. Pretty much everything is hard wire on them. Newer machines that use Pulse Width Modulation over just a couple of wires between controllers is reliable, but more difficult to troubleshoot and way more expensive to work on. When it comes to simplicity and durability, it's hard to beat the H model JLG.

 

[excavator]

I checked out the machine today and found a broken wire in the main cable going up the boom. Nice easy fix, Thanks Willie. Now tomorrow if I'm feeling up to it I can go work on my brother-in-laws 60F that he bought at an auction. Main boom cables were cut, about 12 inches missing so we've pulled new cables in, have it running and operating from the ground. Now it's time to get the basket controls finished up. It's been fun and challenging since it was re-wired once before and the cable wire colors were not at all the same as original and it's also been updated with an LRG-425 Ford engine and there's no wiring schematic for that. But I guess that why we work on these things. Thanks again, Gary

 

[willie59]

An LRG-425 in a F model? Well, that's innovative for sure.

 

[excavator]

I was wrong on that, it's an LRG-423 but they did a very nice installation, looks like they just ordered everything for an H model and installed it.

 

[willie59]

Well, I'm a few enough beers in to have noticed the typo...so it's all good. :drinkup