What color are the wires attached to it? This diagram in the lower center shows a 25 amp fuse for air conditioning. That might be it if it has an orange wire on one end, and a brown on the other end.
If it is a fuse, it should read basically zero ohms with an ohmmeter.
Also, the tach filter is mounted on the firewall, but it has two brown wires on it and it doesn't attach to the air conditioning or the underhood light.