The other two answers are very good, but miss something I wish I understood yesterday.
Access.conf is indeed used by pam_access.so, but so what? You really need to know if pam_access.so is being used during login. Check for it here:
# grep pam_access.so /etc/pam.d/*-auth
/etc/pam.d/fingerprint-auth:account required pam_access.so
/etc/pam.d/password-auth:account required pam_access.so
/etc/pam.d/smartcard-auth:account required pam_access.so
/etc/pam.d/system-auth:account required pam_access.so
Here is the thing: Do not edit these files to add/remove pam_access.so. Other services may overwrite those changes. You have to dive into the dark arts of authentication to change these things... doing so without full understanding can lead to a burned tush.
But the others are correct: changes to access.conf are immediate, requiring no reboot nor service restart.