Computer desk chairs are actually fairly complex devices, with many parts that can potentially fail, according to Gear Patrol, which recommends that a desk chair have at least five adjustable elements. The key will be identifying exactly what the issue with the chair might be and then disassembling the chair and replacing the problematic element. Common problem areas include wheeling problems, seat back adjustment trouble and seat height adjustment.
Flip the chair over so that the wheels are sticking in the air.
Remove any debris that might be stuck in the problem wheel. There may be a pebble or some other object causing the problem, in which case you can dislodge it using the screwdriver.
Lubricate the wheel's axle rod using the WD-40 spray. Sometimes rust or grime may be causing the problem.
Remove the wheel if none of the above works. The axle might be badly damaged or bent, so just pop off the wheel by pulling or, in some cases, using the screwdriver to unfasten. By shining the flashlight inside the wheel, you should be able to look at the wheel rod and lubricate it more accurately. If the rod appears bent, you will need to replace it by taking the wheel into an office supply store.
Tighten the bolt on the back of the chair to fix a wobbly seat back.
Flip the chair over if the lever that adjusts the seat back is not working.
Bolt a small piece of plywood to the bottom of the chair using the existing holes. This will prevent any backward and forward swaying of the chair caused by a loose spring, according to Swivel Chair Parts.
Flip the chair so that the wheels are in the air.
Remove the base of the chair by loosening and removing the small black base retaining clip and the washer on the centre underside of the base. This will leave only the bottom part of the gas cylinder responsible for height adjustment.
Twist the cylinder, using the pipe wrench, to loosen it. You may need to spray the cylinder with WD-40 to help loosen it.
Remove the defective cylinder once it is loosened and take it to the office supply store for replacement.
Reverse the above steps to install the new cylinder. These same steps apply if hydraulic cylinders are used in any of the other adjustment mechanisms.
Investigate the prices of any necessary replacement parts before beginning the repair, because the cost plus the time of the labour may not be worth it. The best option might be to buy a new chair.