Adding rear view camera system to my 1999 E-150 van. Went to the interior fuse panel to locate the 5A fuse for the factory stereo in order to use a switched circuit to tap into for the Rear View Camera System 12v power.. Found it and upon using my multi meter to check the which was the load side and draw side of the fuse (need that info to correctly insert the "Add-A-Circuit Fuse Tap" ) I found only a voltage reading of .04 volts. Not trusting my limited expertise, I had an electrical engineer friend of mine do the same with his meter. He got .042 volts out of the left side of the fuse.
my question is: How is that possible when (not only the stereo) but all of the DC accessories and controls/gaugess etc. require 12V? Also, all of the unused fuse locations had shown 0.00 volts. Did Ford not wire these unused locations so that their van owners would have the opportunity to easily add accessories as they needed. Seems logical to me the the entire fuse panel should deliver 12V not only to the things Ford installed but to blank fuse positions for the owner's future use.

I hope someone out there has these answers because I'm baffled.
Thanks in advance

 

Sometimes there is method to the madness,

Can I suggest something?
Ask your friend what effect voltage spikes can have on printed electronic circuits like the vehicle computer for example..

He should be able to explain and answer all your questions regarding possibly why Ford isn't supportive of adding adding items to the electrical system if certain protective measures are not observed. I'm sure he can provide the correct instruction and precautions to consider better than I.
Would you be kind enough to share some of what he might advise. Thanks.