I just obtained a Caldera Sarasota model from a neighbor, which I believe was manufactured in the late 1990’s. The filter cycle is set to run for 4 hours of every 12. The user manual says this can be adjusted, but doesn’t provide any information on how to change. Anyone know how to adjust the filter duration through the keypad for this old model? I’d like to adjust the runtime to either 2 or 3 hours.