Car fuses protect all vital circuits for the ignition and operation of the car's engine as well as other circuits.
The car's fuse should be the first item to check to revify its status when we have electrical problems.
We can use a 12V TEST LAMP, which you can build yourself with a 12V bulb from 1 Watt up to 5W.
It is very EASY AND QUICK to test car fuses with a test lamp, for this we proceed as follows:
We connect the clamp of the test lamp to the negative of the battery while with the other end we are testing if the test lamp lights up on both sides of the fuse.
A good fuse will allow the test lamp to light at both fuse terminals, if it ONLY LIGHTS at one of the fuse terminals then the fuse is blown and must be replaced with a NEW one OF THE SAME CURRENT.