Give Jeff a call. He will be able to help out. My guess would be that if you unplugged the thermostat, and reset the temperature, and the light is still on, there is a malfunction in your t-stat. When I get that code, it is usually because the electricity flickered. When it happens, you will sometimes get a temperature spike like you noted. However, it usually a very short time period on the temp spike, and it never actually warms up the tub more than 1 or 2 degrees. However, after the error code, I can usually just hit the reset button, and I have no further problems.

I hope that helps,