Fair Value:

[1693TA]

I like the terminal strip idea as there is a lot of strain from wires hanging in free space coupled with vibration of the machine in the original design. Surprises me it got out of engineering, let alone production that way. I addressed each of those coils and the white wrap tape just fell off of each as the oil saturation did away with the adhesive bond long ago. After swishing them around in a vat of board cleaner, then 91% isopropyl and allowing to dry, I then installed small shrink tube over the magnet wire to 16AWG wire connection and shrunk it down. This of course offers great rigidity and integrity to the connection. The one coil with broken wires was the sole one needing resoldered of the leads back onto, but only after ensuring it's resistance reading was very close to the other coils at their respective solder joints which is 21.29 ohms at the then current ambient temperature. A slender bead of non conductive adhesive was then placed across the coil winding to keep it from having possibility of becoming loose finally wrapping the coil with silicone adhesive xfmr wrapping tape in a double wrap. I did order a spool of 28AWG magnet wire to rewind any of these should they present problems in the future. Never have worked with piloted hydraulics in the past, but know the theory well and found your guidance most beneficial. It was in no way looked down upon as too elementary.

No worries about talking straight with me. I built a career being neither politically correct, nor giving a rats ass whom liked, or didn't like me. Not meaning arrogance but I was good at what I did, (as I think you are) and always told it the way it was without exception being sometimes quite blunt with azzwipes whom were management. It can be difficult walking into a problem you've been assigned to repair and have to work with stumped normal maintaining technicians whom are simply at a standstill when you don't know what they've been through. Wanting to do something they've already done nearly always garners or brings out a disrepectful attitude, but this I attribute to frustration, or disappointment in oneself. Sometimes you can change the dynamic, the atmosphere, or the conditions, but one always has to work with what they've got whether positive, or negative. The goal is the same; get something operational that is not, and returned to service. I've always entertained fresh, or new ideas as a new perspective is sometimes quite a useful tool in the arsenal.

You've been a true asset in getting this lift to where it is now; and it is appreciated. I plan to rebuild this until it is reliable as it will be very useful to me in the future and I have the equipment to move it when needed. Those diagrams you had attached have given me both an elementary, and thorough understanding of how the controls and wire terminations work which is enough to attain my goal.

Up to you but feel free to PM your email address and I'll put my appreciation into direct compensation for your input.

I will continue to update this thread as I procede along the path and with this boom raising issue sorted, it should pick up the pace.

Thanks,

 

[OFF]

I'm not looking for compensation. A thank you is more than what's required or expected.
I haven't laid my hands on an "F" series JLG in over 22 years. It feels good to use that knowledge once in a while.
Thank you. & good luck with your machine.

 

[1693TA]

Forgot to mention that I did notice a couple of quick coupler connections with one being on the high pressure filter head, and the other on the boom lift cylinder. Both were under painted over rubber dust caps. These appear to be 1/4" size and I didn't look close enough to ascertain if "A", or "B" series but I have both female style couplers. I only noticed these two, but they will be an asset to easily set system pressures with once I get to that point.

Not about to stab a test gauge onto that test port directly in the well the boom descends into without being supported overhead. Not going to trust unproven safety's at this point. I do not see these shown in the parts diagram for the machine either, so maybe a customer spec item?

 

[OFF]

Forgot to mention that I did notice a couple of quick coupler connections with one being on the high pressure filter head, and the other on the boom lift cylinder. Both were under painted over rubber dust caps. These appear to be 1/4" size and I didn't look close enough to ascertain if "A", or "B" series but I have both female style couplers. I only noticed these two, but they will be an asset to easily set system pressures with once I get to that point.

Not about to stab a test gauge onto that test port directly in the well the boom descends into without being supported overhead. Not going to trust unproven safety's at this point. I do not see these shown in the parts diagram for the machine either, so maybe a customer spec item?

Every cylinder (except steer & axle retract) is protected by a lock valve that makes accidental movement pretty much impossible. Hydraulic pressure is required to release a function before it will move, so don't worry too much about plugging in a gauge. There should be 3 or 4 of those test ports on your machine. A 2500 PSI gauge will do ya. Highest you'll see is about 2100 PSI.

 

[1693TA]

Thanks for the clarification. I had seen the valve shown in the red circle to which I assumed was a piloted check valve requiring pressure to lift the check from it's seat to allow oil flow. This check valve is actually located within the engine compartment by the solenoid valves bank. The check valve shown in the orange circle disallows oil flow should a hydraulic hose rupture and is located in the steel piping prior to the flexible hose connections at the cylinder base:



Very interesting the amount of safety's incorporated into this system, but it very well makes sense. Also interesting the role the "Manual Descent Circuit" plays too. With the boom now up, I can also see that rotary slip ring assembly for access. I will be addressing that shortly to ensure it is conducting adequately.

I need to put an order together for hydraulic hose fittings to get that part moving along also. I have ample stock of 100R17 hose, (3000 psi) but not sure on end types and quantities. I'll have to dig for that as my fittings are in plastic tubs and not cabinets.

Hydraulic shop has all the seals and such for rebuilding the cylinders I haul in; just have to get them extracted from the machine.

 

[1693TA]

Looked all over the machine today and only find the two test ports and they are both 1/4" "A" series quick connects. The boom however is still in the air and another port may be well above my head level. Figures everything I have is "B" series but no problem to get some coming. Found a 3K, two 5K, and a 10K liquid filled gauges removed from equipments over the years so will use them after ensuring accuracy, along with needle valves for isolation and loading. I also have a test set for automotive power steering and another for setting pressures in truck mounted equipments such as dump bodies, spreaders, etc. so can probably come up with something. I don't rob one test setup to shore up another but rather order parts to have a dedicated and complete setup at the ready when needed.

 

[1693TA]

Picked up two 1/4" "A" series quick couplers but only had to pay for a single. They had one that had been physically scratched up a bit so couldn't be sold at retail; hence donated for my cause. Picked up a few other items while there to convert from BSPP to NPT on another project I'm working also.

Snowing and icing right now so may not get much, (if anything) done tonight....

 

[1693TA]

No joy today as the boom lift portion ceased working again. I can still raise and lower it via adjusting the "null", but no reaction from the pushbuttons, or joystick, or toggle switch. I took the solenoids apart again this morning and replaced the "O" rings again, but seen nothing wrong with the former. Deciding to get the oil warm, I then ran the boom all the way down lifting the drive wheels without effort via adjusting the "null" to force the hydraulics to spill over the relief valve with the boom against it's decent stop, and the engine heavily loaded. When the valve bodies reached 125F I backed off the null and tried the pushbutton to raise the boom. There was attempt at operation as it dropped the wheels and took up the slack in the boom sections but wasn't strong enough to raise the boom. I then adjusted the null manually and the boom raised right up.

Getting tired of screwing with this I removed the end plug, (#4 in diagram) to access the main spool. I can depress this spool with virtually no pressure against it's centering spring in the other end. The spool immediately returns to center position as it should. I'm assuming I still have a pilot pressure problem. Looking at this breakout:



"O" rings denoted in figures 27, 37, 33, and 32, have all been renewed, twice. These are the only sealing rings which have been disturbed and/or replaced. Again the originals did not present a problem until the coil wire in the lower solenoid broke free from it's interconnection to the coil itself.

I did not physically watch to see if the main spool moves with adjustment of the "null", but will with the engine not running. I will need to have the end cap removed, (#4 in diagram) to see this action. Can't run the machine with cap removed due to oil flow through the pilot section. #24 in the diagram is a plug right in the pilot pressure passage it appears and I could gauge into it and check for pressure there.

Getting close I know but sure is trying on patience; however I am learning a lot as never have been into one of these before so not so bad.

We'll all have a good laugh when it's all said and done reflecting on how simple the problem was.

 

[1693TA]

Tapped into the boom raise port and this is what I've found:

Little bit of progress after delving deeper:

Finally getting somewhere:

I've discovered the mercury switch is operational also. It probably needs adjusted but I can get the boom to about 14' above the shop floor before it ceases raising.

Thanks,

 

[slceso]

Great read! I'm starting my own journey on a 40HT, mostly functional with a few exceptions. The electric controls I can figure out, but the valve blocks are new to me. Luckily everything is obsolete on mine as well! Regardless, your story has given me the motivation to dig in and fix it rather than push it into my yard and set it on fire. Cheers!

 

[1693TA]

The lift continues to start easily in the coldest of weather and everything is working. Been too busy to work with it much further but I do want to "tidy" up a few loose ends.

When and if you get into troubleshooting those proportional valves a 9VDC battery, VOM, and test leads can be your friend independent upon panel control(s). Many times separation and isolation is a good thing.....

 

[slceso]

...
When and if you get into troubleshooting those proportional valves a 9VDC battery, VOM, and test leads can be your friend independent upon panel control(s). Many times separation and isolation is a good thing.....

instead of the 9v, I was using one of those amazon jump starter batteries that outputs 12v for boost, just to be sure I was getting right volts to saturate the coil. maybe I am overthinking it

 

[1693TA]

You can certainly do that but I would put an inline circuit protection, (fuse) in the circuit you've created. You get a shorted coil with all the amperage a jump starter pack provides and things could not go so well once the smoke stops coming out. A small 9VDC battery doesn't have the "dead short", or "locked rotor" current capacity a starter pack does.

A separate power supply for testing coils is always a very good idea.

 

[1693TA]

instead of the 9v, I was using one of those amazon jump starter batteries that outputs 12v for boost, just to be sure I was getting right volts to saturate the coil. maybe I am overthinking it

There is quite a bit of power available in a fresh 9VDC cell and saturating of a coil works wonders to instill motivation such as shown here:

 

[1693TA]

Great read! I'm starting my own journey on a 40HT, mostly functional with a few exceptions. The electric controls I can figure out, but the valve blocks are new to me. Luckily everything is obsolete on mine as well! Regardless, your story has given me the motivation to dig in and fix it rather than push it into my yard and set it on fire. Cheers!

Well you got my stew simmering again on the lift. I went ahead and found a nickle plated brass marine terminal strip and ordered up 800' of type SXL 16ga stranded wire, (several colors) along with adhesive lined heat shrink ring terminals to rewire this engine compartment housing which is a botched mess. I really don't like strung and unrestrained wire hanging in free space.

 

[1693TA]

Went to move this lift yesterday as needed the space to park a truck inside anticipating the colder temperatures approaching and for some reason I noticed a faint stamping under layers of paint I'd not seen before on the machine frame. Turns out it is the serial number of the machine which up to this point I've not known as the tag is not discernible. Armed with this information I can get correct parts without guessing as the servicing dealer around here is not too happy needing to research for possibilities.

He is going to allow me to take a copy of a point to point wiring diagram of the machine so that should save some effort as it's been a real PIA reinventing the wheel with this lift so far with "OFF" being a great assist.

Wire spools have shipped with the exception of one spool with tracer color. That one will ship next week. Ring terminations have all shipped but the butt splices will on the 24th. That is fine as I have bare splices and adhesive lined shrink tube already. The ready made items are just faster to use.

 

[OFF]

Nice find! When you have a serial number, your JLG dealer can go back to JLG with it and get you all kinda of good information.

 

[slceso]

Nice find! When you have a serial number, your JLG dealer can go back to JLG with it and get you all kinda of good information.

How does JLG dealer service work? when I search on their site, it only shows me Sunbelt and United Rental and the like. Mine is a 1986 40HT and I just figured there was no hope in getting real parts support.

Thanks!

 

[OFF]

How does JLG dealer service work? when I search on their site, it only shows me Sunbelt and United Rental and the like. Mine is a 1986 40HT and I just figured there was no hope in getting real parts support.

Thanks!

Well, I would start by going to JLG.com, there is a place where you can download manuals for your 40HT.

Once on JLG.com, look for a heading:
JLG® Service, Operator and Parts Manuals Available Online

then look for:
"Explore the following online manuals today"

then pick "JLG" out of the choices

then pick "boom lifts"

and that will give you list. Find 40HT, and click on it.

Once you have a parts manual, and find the part number of what you need, Google that part number. It may be available from an "aftermarket" supplier at a greatly reduced price.

And yes, the major equipment rental companies are all going to be JLG dealers, and their parts people can help you. They will like you much better when you have part numbers.

Edit: I see your other post now, looks like you found the manuals. The dealers also have mechanics who can help you with repairs if needed. They can tap into a "tech line" and get help directly from JLG.

 

[1693TA]

Today I received the ring terminations, (#6, #8 in red, and blue) "A" series M&F coupler with dust seals to build a hydraulic test set for for this machine, and several quality environmental sealed toggle switches for the basket which are exposed to weather. Still awaiting the butt splices in both red, and blue. The 16ga wiring, and three different widths of friction tape, (I'm old school) should arrive next week. I have rolls of convoluted loom, (conduit) both split and solid in three different sizes also, but need to order ends and clamps for this now thinking about it.