I talked about this in another post regarding my air horns. I spoke with a technician (engineer) that designs stereo components for cars. He told me that ALL GM (and I guess other cars) are operating at the upper tolerence for the electrical components. The fuses and wire diameters are not able to sustain any additional load without causing problems. I would have thought he was crazy, but when I tried to connect my horns to each circuit, (with a test light also connected) the drain would even cause the light to dim. In addition, the computer sends out signals to test everything, and any added resistance will result in some error message. As hard as it is to believe, the only way is to run a line direct from the battery (fused as close to the battery as possible, then again at the component you are connecting).

New cars are NOT designed to be modified.

 

I don't mean to nit pick, but one fuse will do the job. The fuse should be as close to the source (battery) as possible, as wire between the fuse and the battery is not protected. The current flow in any circuit is the same throughout the circuit so there is no need for two.

One bad side effect of multiple fuses is that a fuse is a resistor of sorts, and does have a voltage drop across it. It isn't much, but it is there none the less. I actually use this voltage drop when checking vehicles for draws. Beats pulling fuses.

 

I use a converter all the time with my laptop. I bought it at WalMart and it is a Vector brand, 175 watt, 350 max. It runs my laptop fine and I've not had any problem with blown fuses...

CBL

 

I would use a high amp fuse by the battery, like 30 amps, to cover anything on the circuit. Next, I would use the correct capacity for each device just in front of it. It may be overkill, but I alway thought that something rated at 10 amps should be fused with the proper fuse, so that it would blow before damaging it.