Just got the same unit from Marine Depot, set it up and mine does almost the same thing except it runs in 15 second increments: on and off, on and off, on and off... and totally ignores the optical sensor. Only cuts off when the float switch is activated and the "too high" alarm is triggered. I keep reading how people NEVER have problems with these but my experience so far has been the opposite. I bought this to have peace of mind, reliability and to be able to keep a larger water reservoir so that I can actually go on a vacation for a week, but now I don't have any
Failures in electrical components do happen, just a fact of life. This unit is traditionally very reliable, and for every malfunction there are thousands of them plugging along happily for years at a time. If you're concerned about it, looking into adding a flow lock and/or a mechanical float valveas a safety option, both seem to work well.
I had the same issue with mine just last weekend, the unit was about 3 years old. Pumped roughly three gallons ro/di water into the sump, the high water level alarm never activated.
Did u open controller and see if switch is changed for alarm.... I am new to this and trying to hook mine up but my pump is bad .... I bought mine used. I am still learning
Mine does the same, except literally only after I’ve refilled the reservoir. Dumps at least 4 gallons into the sump after filling the 15 gallon reservoir.
After sending this video to tunze, they asked me to send them the whole unit. I sent the unit to them and within a week they repaired the unit and sent it back to me free of charge. I’m very happy with the customer service I received from them. Highly recommend tunze. This is the first unit I’ve ever had with any issue. I’ve installed close to 12 of these on my customers tanks.