Furnace making clicking sound when it is already running

Dometic ac and thermostats. On ours there is a setting for 1 or 2 degree temperature delay. Purpose is to keep furnace from cycleing on and off too soon. The relay on this is in the ac, and controlls the furnace also. If set to 1 second, you will hear the relay when it switches on and off before the furnace start delay let's the furnace actually comes on. Change it to 2 degree difference and the problem will co away.