Caldera Aventine no heat!

[kmp]

Hello, I have a Caldera Highland Series Aventine spa. Manufactured 11/2006. 115 volt, single two speed pump. Pump works water is circulating. No heat and temp readings are jumping (103, 104, 106, 108, 109) and "ready" light flashes periodically.  I can adjust temp up and down, but the actual temp is what is fluctuating between 103-109, but the water is cold.  No voltage to heater (put volt meter on both terminals). Replaced high temp sensor and that did not help. Control board looks ok.  Any help or suggestions would be greatly appreciated.  Could this be a bad topside control panel. 

[clover]

The first thing I would check is the flow switch or pressure switch to be sure the movement of water is closing it as it should.  If it remains open or doesn't close, the heater will not operate, thus no voltage to the heater.  The flashing is courious, I would suggest terminate the power testing your GFCI, and then, reboot.

The other 2 components, once you verify circ pump is moving water, would be the temp sensor, and the hi-limit sensor you have already replaced and is a likely suspect.  That sensor is measuring the temp of the water to match the set temp, or call for heat, as needed.  The hi-limit measures the water at the heater, and is not a likely suspect.

[kmp]

Thanks Clover for your response.  In the end pressure and thermistor were not the problem and it was the top side control panel that was faulty.  Since we're up and running hopefully this can help someone else if they ever have that problem.