rothenburger pr 50 pressure test problem

[fcm2507]

hi im newly qualified plumber due to down turn out of work ive just brought a second hand rothenburger pr 50 hand pump pressure tester. could any one help me ive just been testing pipes in an extension and it has worker fine for the fist few runs however now when you screw down v2 it will not pump water it is jammed any ideas will be gratefully recieved sorry its probably obvious but its beaten me.

 

[sparky]

I've had a few of these with same problem. First thought water may be frozen in the mechanism winter time with tester left in van. Used blow torch to thaw and all seemed ok. Other occasions, other times of year had to take to bits put back together problem still there. Sought another pressure tester. Interesting to see if anyone has a solution.