On my air handler, will i get lower than normal amperage readings, if my return air damper shuts or will the motor struggle trying to pull air back causing higher amperage.
When you block off the return air (the damper closes) you are "starving" a typical blower -type fan for air. Less air is available, less work is being done, lower amps will flow to do that lesser amount of work.
[Avatar photo from a Florida training accident. Everyone walked away.] 2 Tim 3:16-17