I have a WaterFurnace ,that is it's brand name. This morning I turned it on and noticed the fault light was on at the thermostat. I went down to look at the furnace control panel and saw the ( Hi Pressure ) led is on. I reset the furnace a couple of time but no change. It comes on weather you use cooling or heating mode.

It could be an air flow problem caused by a dirty filter or dirty coils. I've had both issues, cleaning the coils is not that difficult, there are coil cleaning products availale at Home Depot for this.