To Fred's comments:
The float switch in my HydroHot wore/broke a few years ago. It wasn't something I could dig out of the top of the tank, but if you lower the coolant level to below the switch port, you can remove the switch (the float may not be with it if it broke off). Replacement switch/float assemblies, as I recall, are "rare" but available from certain vendors. My replacement was an improved version as I recall, and less likely to "disintegrate" and or the float leak.
The job was messy, but I finagled a drain line from the drain port down and out an existing nearby hole in the bay floor. Sans that it could've been worse. I probably followed instructions proffered on a YouTube video, but recall my configuration was slightly different, requiring some common sense thinking. I know I was concerned about the missing float part sashaying around inside the tank, but ultimately decided, after failed fishing attempts through the top, that it wouldn't interfere with operations. It's imperative that everything be kept clean, like around the top cap/port and the switch port. You don't want dirt or debris getting in the tank. Properly done, you can reuse the fluid you have to drain to get below the switch port.
It was a matter of getting just the right deep socket as I remember (finally found at Autozone) - and I had to modify it to accommodate the new switch's wires, carefully balled up and stuffed inside undamaged while turning the wrench. Then it was just a matter of hooking up a couple of wires.
I think a person can jumper a couple points on the board and bypass the float switch until you have time to do the repair or get it to a service facility. I apologize for my dim and aged memory, but others here may offer further details. And somewhere I think I have pix of my fix that I'll try to add.
Joel
