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880A Selectamatic Dump Valve

Posted: Fri Mar 15, 2019 9:47 am
by Smokey Joe
Hi, just wondering if anyone could help... Thought I'd try pulling up (opening) dump valve whilst tipping trailer to speed up lowering but instead of lowering faster it virtually stops lowering when dump valve is up. Push it back down and it starts lowering again. I thought if the dump valve was blocked/faulty it just wouldn't make any difference but not actually slow down the lowering? (3 way valve in position 1 and selector in height cos I cant seem to get much to happen with selector in TCU/EXT)..thanks

Re: 880A Selectamatic Dump Valve

Posted: Fri Mar 15, 2019 10:08 am
by ollek
Try to use the dump valve when lowering the 3-point hitch with a load in the lower links. If the linkage lowering speed increases, then the problem is in the quick coupler (male and/or female) in the hydraulic line to the tipping trailer. The trailer end of the quick coupler can, if different standard coupler halves are used, lock up when the flow from the tip cylinder increases, as the dump valve is opened up. A usual fault is a "new" standard female (weak spring) at the tractor and an "old" standard male (strong spring) at the trailer end.

Re: 880A Selectamatic Dump Valve

Posted: Fri Mar 15, 2019 2:06 pm
by Smokey Joe
Thanks, I'll try that on the weekend. I'm using the older dowty style fittings, are these likely to behave like the quick couplers?

Re: 880A Selectamatic Dump Valve

Posted: Sat Mar 16, 2019 9:47 am
by SteveCollett
No the Dowty valves should provide full flow as long as they are screwed up tight.

Re: 880A Selectamatic Dump Valve

Posted: Mon Mar 18, 2019 12:28 pm
by Smokey Joe
Tried it with the link arms and virtually the same... Open dump valve slows arms lowering. I'll be taking the dump valve off to service it but couldn't work out why it behaves like this?

Re: 880A Selectamatic Dump Valve

Posted: Mon Mar 18, 2019 9:52 pm
by philedge
Might be worth sorting out why things arent working under external control as you might have problems other than the dump valve. I dont have a dump valve but my old trailer used to drop fine.