When volume fluctuates, work through this order instead of replacing the valve blindly.
One, the supply side. Confirm tank pressure stability, trapped air and liquid level — pressure fluctuation shows up directly in volume.
Two, the tubing. Check for kinks, blockage or cured residue, and account for pressure loss on long lines.
Three, the valve. Inspect for a partially clogged nozzle, worn or contaminated sealing faces, and a suitable suck-back stroke.
Four, control parameters. Verify dispensing time, valve air pressure and drive speed against the current fluid; parameters often need recalibration after a material change.
In most cases the first two steps locate the problem.
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