I purchased a used jetsetter (1992 J model?) last year and it worked great up until last fall. I drained and cleaned the spa, refilled it and upon refill noticed that the spa was not heating the water. I phoned a friend who repairs them and he instructed me to try to remove the filters and call him back. The spa heated up and I was back in business. I reinstalled a new set of filters. Now it seems to be doing the same thing (not heating unless the filters are out). I was wondering if there's a flow control switch that's sensing restricted flow and shutting down the heater? I dont see one or anything that resembles one in the equipment compartment. I'm a newbie to this forum but I've owned a few spa's that I've repaired and this forum had a lot of good threads that helped.
Any suggestions or comments would be greatly appreciated, thanks!

wally
ps. I've attached an image of the spa guts as a reference.

I just found the owners manual (see below) and I think the low circulating pump (L.-heater circulation pump) also works as a flow switch. Could that be worn? (how do I test it?)

wally

There is no flow switch on this tub.

If it isn't heating, and the jets work normally, it's more likely the thermostat, heater relay, heater, or a burnt wire.

If the circ pump failed, the heater would energize, and the heater high limit would trip in a couple minutes.

Thanks, but why does it heat the water when the filters are removed but doesn't when the filters are installed? (the filters are new)

wally

Coincidence.

The t-stat is probably acting up, and I doubt that the relationship (filter in vs out) will be continue to be consistent.