Dave D

Sorry for not responding sooner, I was away last week. With the water temperature at 87F, the thermistor connected to LIM Therm measures 7.97k. The thermistor connected to REQ Therm measures 8.02k- so it looks like a difference of approximately 50 ohms. I also measured the voltage with the thermistors plugged in & the board powered on. Lim Therm is 2.525V & Req Therm is 2.520V- so it appears to be a difference of 5mV. Thanks, Dave

I replaced the check valve with a straight 3/4" CPVC pipe & used vice grips to pinch off the air bleed on the circ pump output- see attached pic. The tee on the pump output has always been there. Still it behaves the same. Does the controller look for a specific difference between the inlet & outlet thermistors to determine if the flow is good enough to turn on the heater? The in-circuit voltage readings are very close, but not exactly the same. Thanks, Dave

Ok, I'll give that a try tomorrow & let you know what happens. Thanks, Dave

Attached is a picture of the equipment area.The suction side of the circulation pump has a check valve. I can see it closed when the pump is off, then flow inward when the pump kicks in. The pressure switch itself measures 0 ohms. I tried shorting the pressure switch connection on the board, but no change. Both thermistors measure approximately 6.7k with the temperature at 94F. Thanks for your input.

Thanks @RDspaguy. Attached are some pictures. Its been in the upper 90s here in Maryland this past week, so the spa temperature is in the 90s without the heater running. I've got the setpoint @104F. Both thermistors measure approximately 6.7k- when pulled out of circuit - which is about right for 94F. In circuit, they both measure approximately 2.33V. The voltage on the thermistor comes up a few seconds after i powerup & stays at that level - it doesn't change after the lights flash. The power indicator comes on right away, then about 30 seconds later the power & ready indicators start flashing. I can hear the circulator pump kick in within a few seconds after power on & lots of bubbles coming up thru the footwell port. The control unplugged RED LED flashes on powerup, then stays off . The green LIM OK LED stays on. I never see the HTR ON LED turn on.

i removed the filters as suggested but the issue remains. I removed the ozone venturi tube & replaced it with a straight 3/4" pipe. The venturi tube was clean- no buildup. Ran it without the ozonator & filters. How does the pressure switch circuit work? Is it a contact closure? I don't measure any voltage on either terminal of its connector on the board. I'd expect it to have a weak pullup for the controller to sense it. Does anyone have a schematic of the IQ2020 controller board? Thanks for your response.

I also have a Tiger River Bengal with IQ2020 control board- with a heater control issue. After applying power, the power indicator turns on, then the circulator pump kicks in. After about a minute the power & ready indicators start flashing. Everthing had been running fine for a few weeks after I got it filled again ( I winterize it every fall & bring it up in May). The circulator pump went out, so I replaced it. It has good flow- there are plenty of bubbles from the bottom drain with the circulator running ( &ozonator on). Shortly after that the heater stopped & behaving as described above ( flashing power & ready indicators). Heater is fine, measures 10 ohms, but the HTR ON LED on the board does not turn on. The LIM THERM (thermistor) LED indicator above HTR ON is solid green. Both thermistors measure 10k ohms with the temperature at 76 degrees, so I believe they are also good. The pressure switch reads 0 ohms. From what I've read, it should read 0 ohms. Is there anything else I can check?