Hatward H400 heater troubleshooting

[mose]

My pool heater stopped working and I was wondering if someone out there could guide me through the troubleshooting method for diagnosing an "LO" error.

The heater is being controlled remotely. My outdoor control panel is very old, so I'm wondering if I should put the heater in standalone and take the controller out of the equation but I do not know how to accomplish this.

 

[carveitup]

The LO message means that it isn't detecting any water flow. Mine does this when the pump isn't running. If your pump is running and water is flowing, I would bet that it is the flow sensor.

 

[mose]

I will check that out. I have a volt tester that I use for checking battery loads (kids go through batteries like crazy)...Can someone throw me a bone and tell me where to set the meter for testing across the in-line switches......?