I just bought a used Coleman 300 Series tub and it worked fine at the seller's location. I hooked it up to 220VAC, filled it with water, and it worked fine for 2 days. I now have a "FLO" warning on the display and from what I have found on-line, that's why I have no heat anymore.
Where is the flow switch on this model? Can I check it electrically? Can it be bypassed?
Can I check/flush/back-flush the plumbing and water flow to purge any clogs? It's possible and likely that pine needles have clogged something inside the plumbing (I left the empty tub outside while needles were falling--some unseen little rascals may have entered jets/drain lines). Jet motor still works on slow and high-speed though.
Please help--It's cold here in NH and I need heated water or I will have to drain and winterize before first snow.
Thanks ALL

flow switch is on the heater.

it may need to be replaced or adjusted. It's a common problem item.