This is regarding a circa-1999 cal spa tub with a flow-through electric
heater. The controller claims to be a Balboa c2000.

I was starting up the tub after it had been empty for a while.
On power-on, the GFCI tripped immediately. With the heater disconnected,
it powered on. I measured a short between the heater leads and the case,
so i replaced the heater. The replacement heater was a flow-through heating
element, not an exchanger as had been previously.

After replacing the heater, the tub powers on and the pump runs fine,
but there is no power to the heater: the heater LED never comes on,
and there is no voltage across the heater leads. The current water temperature
is displayed as 65deg, with the setpoint at 100deg. No fault codes are
displayed on the panel. I verified that the pressure switch is closed with
the pump on (and open with the pump off).

It seems like the controller is not happy about something, and is not
energizing the heater. But i can't think of what it could be that would not
also cause a fault to be displayed. (There are fault codes for both
low flow and overtemperature.)

Any ideas?
thanks,
sss

Unless it's stuck in economy mode...
Then we're having a $350 conversation.

Main Circuit Board.