Optimus 120-2154 - Manual (Page 25)

3. If the fuse is brown, replace it. Use only the supplied 1-1/4 inch
fuse or a replacement fuse with the proper rating (such as Cat. No.
270-1005). The fuse must be 1 amp.
4. Reassemble the fuse holder by inserting the fuse into the longer of
the fuse holder's ends, and pushing together and twisting the two
parts until they latch together.
5. Reconnect the cable to the vehicle battery's negative (-) terminal.
Replacing the Blade-Type Fuse
1. Disconnect the cable from your vehicle's negative (-) battery terminal
2. If the back of the stereo is not accessible, remove the stereo from
the dash as described in "Removing the Stereo From the Dash" in
Faxback Doc. # 48529.
3. Grasp the fuse's plastic end and pull it out.
4. If the fuse is blown, replace it. Use only the supplied blade-type
fuse or a replacement fuse with the proper rating (such as Cat. No.
270-1081). The fuse must be 10 amps.
5. Grasp the new fuse's plastic end and push it in.
6. If necessary, reinstall the stereo in the dash.
7. Reconnect the cable to the vehicle battery's negative (-) terminal.