I had the same problem with our 1640. The only solution I found for the problem was to disconnect the sensor at the sensor location back inside the screen. The alarm will go off when you start the separator, but that's what the handy little button "Alarm OFF" up by the indicator lights is for. You just have to manually turn off the alarm every time you start it up. The button only disables whatever particular alarm(s) happen to be going off at that time. I took off the chain on my feeder reverser too(since it was just a high maintenance item that was never used) so I needed to turn off at least one alarm anyways. Just need to watch your temps in case you start to plug up the hyd. cooler or radiator.