I have a Coleman Horizon Series 400 spa that started the above message and no heat. The message alternates with the tub temperature. I've tried removing the filter but the error message stays on. The two pumps both run strong with what seems to be good pressure. The tub is probably 10 years old. Is there a generic pressure switch that can be used for replacement, or do I have to remove the old one to see it's make and model. (I am a customer, and recently ordered a cover for the spa from your company.) I've tried resetting the breaker also to no avail? I'd consider replacing the whole heater assembly as this tub is getting old?