Oh, now we know it's a Keystone! How about year and model - perhaps include that information in your signature in the side panel?
I already responded to you earlier post... maybe a moderator can combine them.
Meanwhile - most likely it's a fault indicator that the propane side of the water heater has failed to light - or has not lit yet when just starting - that means you'd have to check that your propane has gas, valve is turned on and air has been purged from the lines so the igniter can fire up the water heater. I think all coaches have that fault indicator somewhere - Ours in built into the propane selector switch for the water heater on the control panel.
