Sundance Majesta Hot Tub Heating Issues

[TerenceOB]

I purchased a house at the beginning of August that came with a 2005 Sundance Majesta Hot Tub (Sentry Controller 850 LCD 6600-098 Rev D)

I kept it around 90F for the summer until a few weeks ago when I increased the setting to 100F, but the temperature never got over 95F. The heat indicator would show on the display, but the water was not heating. Initially, a full power cycle would kick it back on, and then activating and deactivating the high speed jets. Since there were no errors, displaying but the heat indicator was on, I started with replacing the heater (and the high limit sensor that came with it). The replacement had lights for power and high limit, and the power light was not on when the heat indicator was showing on the LCD.

But then I noticed that when the spa made a call for heat, the power light on the heater blinked. I hooked up a multi-meter to the heater terminals and was able to confirm that when the spa calls for heat, 240V is sent to the heater, but then immediately cuts off and the reading is 0V, even though the heat indicator on the control panel stays on. Just to see what would happen, I disconnected the heater and power cycled the spa. I got 120 volts reading from the heater terminals regardless of whether the LCD indicator was on or off.

I’m not sure where to go from here with my troubleshooting - board or sensors. It’s clear that the circuit board is cutting power to the heater and there are no errors. If I disconnect the flow or high limit sensor, I will get the appropriate codes on the LCD. From what I've read, if the heater isn’t getting power, then it’s the circuit board, but its not completely dead because it does get the initial power. is there anything else I should replace / rule out before I do that? Are there any situations where the circuit board isn't bad and the LCD indicates the heater is on but it's not being powered?

Any assistance would be greatly appreciated.

 

[RDspaguy]

got 120 volts reading from the heater terminals regardless of whether the LCD indicator was on or off.

As you should, since one leg of this 240v heater is always on unless the high limit is tripped.
Any condition that would turn off the heater, other than reaching set temp, would also display an error. As far as the controls are concerned the heater is on.
So it's a relay or control circuit, most likely a relay. These can be replaced by most electronics/computer repair shops for considerably less than a new board.

 

[TerenceOB]

As you should, since one leg of this 240v heater is always on unless the high limit is tripped.
Any condition that would turn off the heater, other than
So it's a relay or control circuit, most likely a relay. These can be replaced by most electronics/computer repair shops for considerably less than a new board.

Thank you so much for your help, and you were correct - it was a bad relay. Couldn’t tell on visual inspection which one was bad, so I just went ahead and replaced all three K relays . Took a little longer that I thought (soldering isn’t like riding a bike), but once everything was wired up again, heater light came on and stayed on.

Thanks again for the quick replay and all the time and money you saved me. Not all heroes wear capes.

Terence

 

[Mdragger88]

@RDspaguy is our very own hot tub hero for sure!