Help - 2004 Sundance Marin 780 FLO (not heating) Error

[Tahoe]

Hi all,
Looking for help with diagnosing why my tub wont heat past ~60F.

Error is a blinking FLO that is alternating with 'COOL' and the temperature.
All pumps/jets/ozone bubbles seem to be operating normally.
The FLO switch closes (and stays closed) when the tub gets power, and opens when the tub is off.
Took hose off the bottom heater and the circ pump is pushing water that way but I don't see any indication of it in heating mode on the control panel, wondering if it could be the heater? But why the FLO error then?

Wondering what other things I can test and check before I start buying parts!

Thanks!

 

[RDspaguy]

The FLO switch closes (and stays closed) when the tub gets power, and opens when the tub is off.

Tested with a tester, or just visually? The flashing flo says it's not closing. So you have a flow restriction or a faulty switch/wiring.
Remove filter. If it works get a new filter.
Check circulation pump for adequate flow.
Test flow switch with ohm meter.

 

[Tahoe]

More background: Spa was accidently turned off and froze over when all problems started.

Visually.
Removing filter does not fix problem.
What is considered adequate? It's definitely pushing the water into the heater but not sure @ what GPM. I can attach a hose to it and see how long it takes to fill up a 5gal bucket?
Just test for continuity?

Extra new issue: My heater just developed a slow leak (seems to be through the gasket).... thoughts on replacing a heating unit in a sundance spa with something aftermarket? Amazon has a smart low-flow heater 5.5kw for 1/3rd of a OEM.

Thanks for all your insight

 

[RDspaguy]

Flashing flo means the system thinks the switch is open when it should be closed. So, the flow switch is not closing (likely flow restriction), is malfuntioning, or the circuit board is bad (highly unlikely). That's it. So test the switch.
Having never used a non-oem heater on one of these I cannot advise you on that.