Hyd slides - what controls the ext/ret function?

[danandbetty]

I know the subject of slide problems has been discussed unendingly but i can't find any discussion specific to the problem I'm having.

Here's the problem: The slides on the hydraulic side sometimes don't retract when the switch is depressed. The pump's electric motor runs fine every time (its not the auto breaker problem that so many have). The hydraulic reservoir is full and no air is in the system. Also, the slides work perfectly every time when extending them so I assume the pump is working correctly. The problem only happens on retraction - and it's intermittent.

I thinnk the mechanism that redirects the hydraulic fluid (elect controlled valve?) is not funtioning properly. I don't know how to determine if it's the elect switching at the valve housing or the physical valve(s) that's causing this problem.

I did a continuity check of the wiring between the operator switch on the wall and the unit - all checks out well (if I understand it correctly). I jumped power between the positive terminal and each side of the switch assy on the pump housing - sometimes there's a 'clunk' (the valve repositioning?) but not always. Seems like I should be able to switch it back and forth and hear it but it doesn't happen always. Worn out valve? Worn out elect switch (or whatever moves the valve).

Can anyone explain how that system works? Anyone know an easy way to determine the what exactly to repair or replace? Anyone have experience with this particular problem? Any tips on disassembly/reassembly (Is this rebuildable or is it a remove and replace situation?)

I appreciate hearing from anyone with some technical knowledge of this system. thanks ahead of time....dan