4-post lift quit lifting. Automotive lift not working. Auto lift repair. Hydraulic lift repair 101

I got up this morning to work on the C4 Corvette and discovered it was stuck up in the air. Yup you heard me right, in the air. When the lift is resting on the locks, you actually have to go up a little to release them before you can lower the vehicle. This time I hit the button and...nothing. I could hear the motor whirring, but nothing was happening. After a few attempts, I headed to the house and consulted all knowing You Tube. There is a surprising lack of information on problems with automotive lifts. I managed to find one of a guy not unlike myself just disassembling his lift without having a clue of what he is doing. When he put it back together, it worked but unfortunately, he had no idea what fixed it. Since I prefer to check the easy stuff first, I started with the relief valve and worked my way inward. Watch me as I use the process of elimination to find the problem and fix it in less that 10-minutes.

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My first thought was you didn't have enough fluid in it. If there's a small leak over time you'll eventually get to a point it stops working at top of travel.