jpi72 - can you post a picture of the 621 that you are working on? AC released and revised the 21' lift on a reversed D15 Farm Tractor, they also released and revised over time their 21' lift offering including an I- 60 with a 21' lift, and I-600 with a 21' lift and a later model referred to as a 621. AC Form TPL-554 is the Parts List for the Industrial 60, and Industrial 600 Fork lifts. It would be helpful to have that as a reference.
The steering cylinder attached to the axle used on the I-621 forklift has a supply and return line connected to an orbital motor or as AC refers to it a (power steering control valve) located at the bottom of the steering shaft. Without being able to see the unit I would guess that the return and supply lines could be leaking enough and possibly have leaked enough so that you have no remaining pressure to move the steering cylinder. What does fresh cardboard show when you leave it overnight underneath the steering shaft and the steering cylinder - any leakage?
What are the ambient temperatures where the unit is stored or parked? Is it freezing - I would guess also if the system has not been drained and refreshed that there is moisture in the system and perhaps has frozen and has turned to ice. If hydraulic supply is low you might not be making the necessary pressure to move the cylinder to allow "power steering" to work at all or even partially.
Also, if you have access, to the supply line you could plumb a T into the supply line and hook a pressure gauge into it to see what pressure you are carrying. Will check my AC library to see if I can find a pressure criteria for the 621 steering cylinder.
HTH's ~ Orangeman
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DrAllis wrote:
