The BTC unit inner carriage will not lift or drifts down when raised.
A check valve located beneath the pump piston barrel contains the oil pumped into the cylinder. If the barrel has become loose, the oil is able to bypass the check valve allowing the cylinder to drift down. Retightening the barrel will normally resolve this issue.
BHS recommends performing the aforementioned procedure prior to rebuilding or replacing the manual hydraulic cylinder. If the cylinder continues to drift after performing this procedure, a cylinder rebuild kit or a new cylinder from BHS may be required.
Refer to Technical Procedure TP-609 for piston barrel tightening procedures.