While we're on this subject - I was going to run a control circuit out of my fuse box to control a relay for some new driving lights and I could not figure out how to connect into the back of the fuse locations? I have several open fuse spots; but, how do you connect to fuse terminal?
For trucks with double spade fuses, I start with an empty slot at or above the correct amperage (fuse box cover, owners manual, Ford Service manual will give this information) With a test lamp and no fuse in the socket I will test each side of the socket to determine if it is always hot or hot with ignition on. I will next cut a piece of copper shim stock to wrap around the leg (plug end) at the load (fused) side of the fuse to allow enough copper to extend past the top of the fuse. At this point you can use a wire with a female spade connector to mate with the copper fuse extension. You can buy fuse extensions from Radio Shack or make it yourself. A connection from the back side of the fuse block is far more involved but does require the same test steps outlined above. If the load side of the blank socket has no wire, you can solder your new wire to the fuse base. If it does have a wire on the load side, simply cut it far enough away from the socket to allow reconnection later. Solder your new circuit wire to the one you cut comming from the fuse base. Install the correct size fuse and you are done.
Thanks for the info - my fuse block does not have any wires coming off the unused fuse spaces. I could not see any way to connect to the fuse block - I now understand that I would have to solder a wire into the block - that looks like a difficult job due to the fuse holder being so far down into the fuse block. I was hoping I could get a "Quick" connector to slip down into the block to connect to the fuse holder.
Oscar is right, the task is a bit daunting at the onset but like most fabrication projects there is a work around. Since the socket is embeded deep into the fuse block (as viewed from the back) and most do-it-yourselfers don't have a soldering tip that can make the reach let alone add solder, this is my work around for a clean factory look.
The fuse block must be unfastened from where it is mounted to do this task, although it can be done inside the vehicle while lying on your elbow (not comfortable)
If you have a narrow soldering tip you can stick it into the front side of the fuse block into the "load" side of the fuse socket. Allow the temperature to rise enough (not too long) for the socket to sufficiently melt a small bit of flux core solder into the base. Allow to cool. Test the socket with your fuse before you continue. Too much solder will not allow the fuse to be inserted. If this happens, just reheat the socket and push a small blade screw driver into the slot, then remove immediately.
Next strip enough insulation from your new wire as if you were going to add a terminal lug. Slide the stripped end of the wire through the back of the fuse block into the "load" side socket of the fuse you wish to use. With your other hand, press your soldering tip into the front side of the socket while applying pressure to the new wire from the back side with your other hand. You should feel the wire move very slightly when it has entered the socket base. Quickly remove the soldering tip but keep a firm grasp on the new wire until it has had sufficient time to solidify and not pull out from the back side of the socket. VIOLA! A new circuit!,
Now then, if you do not have a soldering tip that will reach down into the front side, unused fuse socket you may try this; although it will work, I don't recommend it.
You will need a cold soldering tool, (yeah the ones they advertise on TV for $ 19.99) because they will start cold and return cold very fast. You will be soldering a wire to the "inside" of the load spade on the new fuse. The inside will be viewed as the fuse is lying on a bench with the colored plasitc part at the top, and the spades on the bottorm. The "inside" will be the area between the spades. The wire must be soldered to the inside section of the spade so it can pass through the fuse block when the fuse is inserted. Once the fuse is inserted into the socket, crimp or solder a male spade or barrel connector to the other end of the wire you soldered to the fuse. Be sure the wire is plenty long enough to remove the fuse so you may be able to resolder this same wire should the fuse blow. This is why I don't recommend this type of work around. It is annoying enough to have to replace a blown fuse, let alone having to round up a soldering tip and solder as well.
Another method which is less effective, but still works, is a reverse extension. A reverse extension is like the fuse extension I wrote about earlier. The reverse extension is made from a piece of copper shim stock the same width as the inside of a female spade connector and long enough to bend into an "L" shape. The bottom of the "L" will rest inside the load socket for the fuse and the shaft will extend through the hole between the two sockets and protude through the back of the fuse block. Some fine trimming and twisting of the copper will be required, but once you have it, you are almost done. Insert the extension, insert the fuse, then carefully push your new wire with female spade connector over the extension. Done!