MrWizard wrote:I have a document that explains the operation of that switch somewhere but cannot find it now. But what it said is that the 'system' won't operate if the pressure doesn't CLOSE that switch. So it's like a minimum pressure sensing device. If you're low on oil, the jacks won't operate...or something.
so if the switch fails completely, you can stick 1/4 - 26 NPT plug in there and jumper the wire to ground, to have emg use of the system without fluid loss
cole parmer 25lb N.O. pressure switch
Or just jump the switch
I have a document that explains the operation of that switch somewhere but cannot find it now. But what it said is that the 'system' won't operate if the pressure doesn't CLOSE that switch. So it's like a minimum pressure sensing device. If you're low on oil, the jacks won't operate...or something.
so if the switch fails completely, you can stick 1/4 - 26 NPT plug in there and jumper the wire to ground, to have emg use of the system without fluid loss
cole parmer 25lb N.O. pressure switch
MrWizard wrote:
jim you got a picture of that switch ?
where is the switch mounted, and what does it do ? according to hwh info
i worked around industrial hydraulics and machinery controls for my CNC career
50 PSI is like air pressure level, way low for hydraulics
could this be low pressure cut off, if you dont have a minimum of 50 PSI the system defaults to NON-OP and won't try to activate the jacks or slides ?
way to low for an over pressure alarm on hydraulics
pull the wires off the switch
read continuity of the switch, is it open or closed with the system off
where is it leaking ? at the threads where it screws in ?
might just be and 'O ring' seal
It is mounted to the 'Jack' section of the HWH hydraulic manifold.
Here's a picture of it attached to the manifold:
It's that brass colored device with the rubber cap removed from the end. That's where the oil was leaking from. I clean the oil off...it's not much...and have used the jacks several times since then and the leak is very minor. I do want to be ahead of it though.
Here's the switch after I removed it. The jacks are deployed, and when removed, maybe 1/2 teaspoon of oil came out of the manifold and the jacks stayed in place, did not retract.
The oil pressure switch is 3.5" long, the business end that is screwed into the manifold is 0.4" in diameter (includes the threads) with 26 TPI screw pitch. It's not leaking there. It is a Normally Open (NO) and it measured open before I removed it today for the pictures. The other end is plastic with a hole for the wire, and it seemed that the oil came out of that hole. There was Teflon tape on the threads when I removed it so I doubt that there's any O ring in that manifold hole it screws into.
I have a manual and it shows it as a 90 PSI Switch in one place, and 50 PSI in another. Pages have different dates. Both pages and the drawings are for the 'leveling' system separate from the room extension system. The hydraulic schematic shows it at 90, the 'Manifold Diagram', which is a physical drawing of the manifold, calls it 50.
I have a document that explains the operation of that switch somewhere but cannot find it now. But what it said is that the 'system' won't operate if the pressure doesn't CLOSE that switch. So it's like a minimum pressure sensing device. If you're low on oil, the jacks won't operate...or something.
I can use a 75 PSI switch I found at Carquest no problem, even though it's a NC. But of course I'd prefer a NO, but at only $8, hard to beat the price, and I can adapt about anything if it's in range. They are trying to find a part number for me now. Spent 1/2 hour there yesterday and they couldn't find a NO device.
