We recently purchased a jacuzzi j-340 hot tub. All the jets/pumps seem to be working fine. However, the heater will not enable due to the FL1 error. We have drained and refilled, replaced both filters and checked for air gap. We also replaced a flow switch - still no luck. Any ideas ?

Do you have a low flow heater or a flow through heater? You can tell the difference by the size of the lines feeding the heater. Low flow heaters usually use 3/4" poly hose for inlet and outlet, whereas the flow through are typically 2" diameter stainless steel and right in the main plumbing. A low flow will use a dedicated circulation pump to feed the heater, and that pump could be defective on your system. I am not familier with your model, that is why I offer up the two options for heating, as I don't know which yours uses.

i believe it is the low flow type. At any rate, my husband had someone come last night and look at it. He says - bad circulation pump - supposed to call us today with cost for new one when he orders. Hope it isn't too outrageous.

thanks for your help - sounds like you were right on the money.