35QSQB #2 Graywater valve

y #2 graywater valve is stuck open and I cannot currently take it in to a shop to be repaired as we are on the road. I don't want to remove the entire underbelly to find the valve, so I was hoping someone could help me out and give a general area to loosen up so I can fix the gate valve.
I have not tried back flushing yet, but I did inspect the back of the cable behind the dump control panel and it looks good there, unfortunately, from there the cable goes down through a cutout into the underbelly and I can't see where it reaches. The only thing I have been dissatisfied with was the owners manual and the lack of technical drawings. I am a Chief Engineer offshore and I would say roughly 95-99% of all items (motors, pumps, etc.) come with drawings and exploded view diagrams and if they don't, the company will usually email them to me quickly. The owners manual seems to be a generic book for all Heartland trailers and is relatively unhelpful when it comes to the specifics of my unit and Heartland is unwilling to share those diagrams. I understand saying that it could void my warranty, but when your on a trip, you don't always have the luxury of dropping your trailer off for three days for a 1-2 hr (max) fix. At least for the next 5 weeks it's our home. This is not written to bash Heartland in anyway, just a personal frustration.
From the original1Gate Valve.com
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