FLO and PLUG message

I got a optima that I just replaced the heater(It froze and cracked the housing) everything else seems to work fine on start up but then I get a FLO or PLUG message on the screen and the heater is not working. I do have 240 going to the heater. The dealer here does not return calls and is never in the shop...I have left 10 messages with his secretary.. I have rebuilt a hot springs and am very comfortable working on tubs so if anyone can point me in the right direction please do. Please help!!!! Thanks

[Mary]

If you are getting PLUG as an error message that means that the spa top side panel is not making a good connection. I would turn the power off, unplug panel and then plug it back in, turn power back on and see if it clears. On a FLO error message it could mean a few different things. It depends if it is flashing FLO or stays on solid. When the spa is in FLO the heater will not come on. If it's flashing then that means the flow switch is not closing due to reduced or lack of water going to the spa heater. This can be caused by a dirty spa filter or the 24 hour circulation pump has stopped working. If it is a solid FLO then that means the flow switch is stuck closed, maybe something wrapped around the paddle not allowing it to open back up.

Also, when testing power going to a 240V heater, you should test across the red and black wires to verify 240V, not one leg to ground. If the spa is in FLO you should not be getting 240V to the heater.