Those older HWH systems used a large bolt welded to the chassis and brought all the system grounds together at that one point. Over time, it would get corroded and parts of the system would lose the ground that allowed it to operate. So you could have symptoms all over the map as different parts of the system lost their ground. Vibration could bring it all back. Cold weather would cause systems to fail, and as it warmed up during the day, they'd start working again.
With all that in mind, check under the RV near the hydraulic manifold for a large stud with numerous white wires with ring terminals all bolted to it. Winnie uses white as the ground lead color.
Remove the nut (if you can, sometimes it's rusted on so tightly the bolt breaks off) and clean all the terminals. And clean the bolt and nut. On my RV, the bolt snapped off so I had to drill a couple holes and make new attachments for the ring terminals nearby.
Here's my ad free article about it:
HWH Hydraulic Slide Control... | Chaos Leaves Town
And here's a picture of the grounding stud below the hydraulic manifold of my '02 HWH system.
I missed that stud several times as I tried to find a cause of the intermittent operation of the slides...but my jacks always worked. I always worked on it from the upper right side and that stud is low down on the left towards the front area...but underneath.
Once all those terminals were cleaned and a new ground made for them, haven't had any more trouble with the slides or jacks. Oh, wait, did have an inline 40 amp fuse and socket right near the manifold that was so corroded it just open circuited one day. Entire hydraulic system shut down suddenly. I was at an RV park so extended my stay since the slides wouldn't move in. Had to replace the entire fuse assembly but Napa carries generic stuff that worked fine.
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