questions about fuse #18

[jokken]

hey guys I discovered something this weekend that I'm not sure if it is correct or a problem.

i was trying to find out which part of the fuse receptacle that the power comes to from the battery and which part goes to the device being powered.
Using a volt meter I noticed that the top connector was getting 12 volts and the bottom was getting about 3 volts, is this right?

This is the #18, 20AMP, radio/CIA fuse in the fuse box behind the kick panel on the passenger side.

I would assume if the top was coming from the battery it would be getting 12 volts and if the bottom was going to the radio/CIA it would have no voltage.

this was with the fuse out and with the key in the on or off position.

any input would be appreciated

BTW what is CIA, and what does this power line do for the radio? This has power with the key on and off (after I open the door) so I know it isn't for the radio main power (plus there is another 5AMP fuse for the radio, fuse #9 or something)

 

[TheRebel]

If it was the radio fuse then you were prolly reading the 3 volts from voltage stored in the capacitors of the radio and the 12 volts went to the battery

 

[fonsito]

and this means???

 

[cpgoodman]

The capacitors hold some voltage from the radio even when it is not in use. They are like mini power caps for an amp. Same concept. They hold voltage so stuff inside the radio holds its data. So the 3 volts you are reading are like the other guy said. They are the reading of voltage left in the capacitors.

 

[jokken]

ah that makes sense, thanks guys.

to confirm this is there a safe way to discharge them so I can check I get no voltage then?

 

[TheRebel]

you can go to radio shack and buy a small (prolly 100 ohm resistor will do) place one end on the 3 volt side and the other to ground.

 

[fonsito]

Other thing is disconnect the battery to see if then you have voltage