When I got my 1702T it came with a large envelope with all of the booklets and product info sheets. One of them was a large fold-out sheet for the Hydraulic Pump and Motor. Since I was working on the lift cylinder at the time it seemed smart to check it out. This thread is for info.
1. Pump: My pump had a nameplate that said: Monarch Hydraulics, Grand Rapids, MI, M3519, 12 volt. The info sheet had the website of: monarchhyd.com. So off to Google for info.
2. Website: Got the website and clicked Products > DC Power Units > Monarch Hydraulic Packs > Technical Info and there was the click to my Pump, M3519
3. At the technical Info page you could click to a 27 page trouble-shooting Guide. Lots of info here.
4. I talked to a Hi-Lo repair rep at Stahmann RV in Texas and he said in 16 years he only worked on 2 pumps and replaced 1. They seem High Quality, reliable, trouble free, etc. All of the owner problems were with wiring, batteries, switches, guide rods, and cylinders.
5. When I clicked on my M3519 pump sheet there was a complete parts list and exploded diagram of the pump. Here are the pump components of interest:
a. Vented Plug in the reservoir
b. Spring Loaded ball check valve to prevent back-flow
c. Adjustable spring loaded relief valve to prevent over-pressure
d. Solenoid coil lowering valve downstream of the ball check valve.
e. Manual lowering valve in case d. does not work or you want to lower the top from the pump. Turn counterclockwise just like a car jack.
f. Built in filter in the reservoir.
6. Note that the lowering valves are in the pump. This means that one line to the cylinder is used in raising ( fluid under pressure flows to the cylinder ) and in lowering ( gravity pulls top down causing back flow to the reservoir ). One aluminum line is all you need since fluid flows both ways.
7. The pump is a high pressure, low flow, positive displacement type. Fluid is ATF Dextron or equal.
8. These pumps seem to be everywhere there is a load to raise or lower. They are used for agricultural, cemetary, RV lifts and slide-outs, military, garbage trucks, construction, etc. That is why they have so many variations such as high and low speed, AC and DC, Fast and Slow lowering, etc.
This thread is for info since nobody to call at factory since closed. My pump seems to be working fine after 9 years so fingers crossed.