ot hydrailic nightmare

[ericlb]

maybe someone on here can help im loosing my mind on this truck, the truck is a 70 f350, but it has a utility brand hydraulic ladder and bucket on it, its a original rig, and so old that utility body company doesn't have any info on the serial number, whats happening is the ladder boom, will raise with the electric switch which activates a hydraulic ram, but it will not lower, its been a intermittent problem for awhile, usually solved by shaking the wiring, and a good solid hit to the truck, but nothing happens now, it has a row of 3 electric solenoids ,3 facing up. 3 more facing down, one over the other, now the hydraulic line goes to another, what i call a directional valve, but im not sure thats what it is, the electric w2ires go from the solenoid to this part, it has only 2 wires, but at this time both wires are hot, this part must have a valve in it to make the hydraulic fluid raise the cylinder or let it down, its a one line cylinder, so, gravity down , but hooked up, nothing is happening, im lost as to what i need to do, now the other change is these electric solenoids are pretty audible when the switch calls for them to function, now one is softer, but its on the raising side which works, the down side is louder, but does nothing,i needed the truck today, but right now the ladder is about 16 feet in the air, so its not going anywhere

 

[ericlb]

should add i have made new connections on the main wiring into the switch box and all of that has power to it

 

[Steve@Advance]

If you can hear the down solenoid click, that means it is getting the electric signal to it.

If it's not clicking, try running a jumper wire from the battery to one lead, ground the other lead. If it clicks but still nothing happens, there is a problem in the hydraulics.

At no time should both wires have voltage, always one coil or the other energized, never both at the same time. Typically the coils have a common ground.

Just a guess, the other hydraulic block is a safety to regulate the down speed. It monitors flow, as in a broken line, to slow the descent so the boom won't fall if something goes wrong. It could be stuck.

Be careful, cracking any line or removing any valve block can make it fall!

 

[Dune Country]

I worked on those years ago, even went to the Pittman school.

3 solenoids, up/down, right/left, in/ out.

picture would help, but some had a velocity fuse for the down, some had a check valve, ladder would go down slow if the hose broke.
Some had a button on the hyd. manifold for manual lowering.
You could always crack the hose on the cylinder to lower it so you could move it, messy though.

 

[ericlb]

thanks guys im going to go out at look at that there is a additional block onthe piece that the hydraulic hose goes to from the cylinder which has a adjustment thing on its bottom that must be the safety

 

[David G]

Be real careful with it, block well.

 

[Ken Loewenhagen]

If all of the solenoids and valves are working, it might be a holding valve. A holding valve takes pressure to open and let oil flow through it. I've seen those go bad. When they do, they won't unseat and the oil can't get to the cyl.

 

[SkipperII]

It should have a holding valve at the base of the cylinder, if I remember correctly, try energizing it with a jumper. If that doesn't open it, you may have a bad coil in the valve. I seem to remember that you could lower it manually by screwing a valve on it, can't remember if it was in or out, but count the turns.

 

[PJH]

Pilot operated check valve

 

[ericlb]

well i couldnt get it to work, i did lower it by cracking the line and gently letting the boom down into its rack, this may be one of those things where one thing leads to another, the up function now only works with the override button, that being the case, no more than i use this thing, [a couple times a month maybe] if i keep the safety valve in the line can i use a log splitter type manual valve to bring the boom up and down? granted its not the best way of ding things, but that would let the truck function, better half still isnt over the 250.00 i spent on brake parts for the truck, which arnt even here yet, hopefully i get to open one of those big rear drum boxes while the delivery guy is still here just to show him what he carried lol

 

[ericlb]

also if i do order solinoids and the valve, im going to have to get with you guys and see where to get those if they even still service those, this is a 1970 body,

 

[MARK ROBKE]

If both wires are hot, it has lost it's ground. Fast way to test: unhook both wires, hit the switch, only one will be 'hot'. Rehook the hot wire, ground the other wire. It should work. When those solenoids are activated, they should be magnetized on the end. Mark.