I think Frank said it, Steve. The float switch, if that's what's wrong, is not something a normal hydroponics service would be expected to check. For one thing they'd have to at least partially drain the internal tank to remove the switch for examination, and even then it may not reveal a hidden weakness. Units of our era used a switch with a plastic arm that is what failed on mine. The replacement for it today is a stronger model.
And I have to add that replacing the switch would be a relatively easy task except for the need of a special socket because the switch's wires are in the way of a normal socket. In my case I bought a super-deep socket so the wires would fit up inside it, out of the way of the socket fitting down over the bolt head. Even then it took a lot of finesse, trial and error, and a little advice from the fellows here. See the two yellow wires coming out of the switch in its pocket in the foil insulation? The spade connectors seen below them unclip easily, but then those few inches of double wires and two spade connectors have to be stuffed into a socket wrench socket. Or you have to cut special slots in the side of a socket to run the wires through. Yeah, you can just clip the wires off at the switch to readily remove the old one; but then you're going to have to put the new switch in without damaging its wires.
You may not be able to save the drained fluid without contaminating it in the process, due to the confined area you have to work in. New fluid would be advisable, but be sure you mix it correctly. And be sure you use the Camco Boiler fluid designed for hydronics. You may want to get a fluid refractometer to test the old fluid remaining and mix the new correctly. The device is handy for other fluid tests also, like battery acid and antifreeze. Then its always fun trying to pour fluid back into the filler neck with such limited access!
i.e. - You may find it best to have an experienced hydroponics technician do the job, rather than pull another muscle trying to maneuver in there.
That all said, as noted here previously, the tank's filler neck has been an issue for others here. Apparently the extension that holds the overflow tube or the weld to the tank can weaken and fail, causing fluid loss through leakage and loss of proper pressure. While I had mine off to fish for the broken off switch part (forget doing that, it doesn't hurt anything floating around in there and even if you spot it you'll never fish it out), I examined the filler neck and hose for bad areas, but it all looked good.
Joel
For reference if needed: John Carillo may be the best source, as it was for me.
https://www.heatmyrv.com/product/float-switch-brass-ele-800-002/
