You would need to know the weakest point in the power distribution and you'd need to know the peak and nominal current draw in Amperes. If it's a device that uses a surge of current at startup but only a fraction of that during normal operation, you would need a "slow-blow" fuse. If the current draw is consistent you would need a conventional fuse. Still have no idea what the "head unit" is that you're trying to fuse.
watts Divided by Volts = amps
The correct size fuse is determine by the size wire used in that circuit. In a kitchen you would use AWG # 12 wire which requires the use of a 20 amp fuse. An electric cloths dryer would require AWG # 10 wire with a 30 amp fuse. The fuse or breaker always corresponds to the size wire not the appliance being used.
Open fuse box, locate correct fuse using the fuse diagram, and replace the blown fuse. www.nationalautoinc.com
find correct fuse for 2003 Toyota Camry XLE for ignition system
The relay just plugs into the fuse/relay box, installing it means reading the owners manual to determine the correct location and plugging it in.
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Replace a blown fuse with the correct fuse that it calls for. There is a reason the manufacturer put it in there.
The fuse will blow as soon as you turn it on. Use the correct fuse and nothing else.
Use the correct fuse and nothing else.
Normally it's located under the hood in the fuse box next to the battery. Under the cover should tell you which fuse is the correct one.
Read the label.