Truck just arrived (see my intro thread here-- new-520-owner-t569889.html?).

I did a quick check of things and there a few issues I am going to have to deal with before I drive it. The biggest one is that the brake lights don't work. I did a quick debug under the hood and saw that there are no wires attached to the brake switch (see pic below). Well, at least I know WHY the brake lights don't work. My question is, what wires in the harness SHOULD be connected there? Also (possibly related, possibly not), there are 4 wires running across the firewall to the driver's side that just dead-end. a pair of greens and a green/black pair. One set has male bullets on it, the other has females (as though they should be connected to one another). Somebody slapped a couple of blue bullet crimp caps over the males, presumably so there wouldn't be bare metal. However... it seems odd that Nissan would have run wires from passenger to driver side just to connect them to one another. Methinks something is missing. Any help would be greatly appreciated.





And then... one terminal on the fuse box is bare. Any idea what should have been there???

I made a large format print of the 520 wiring diagram I found here and have run through the wires. What I found was odd. In addition to the brake light PRESSURE switch under the hood, there is a mechanical pedal switch (and it looks very factory-ish). The green/yellow wires, which are in the harness just above the pressure switch (where I would expect them) have been doubled back into the cab through the hood release grommet, and then tie into the pedal switch. Ultimately, it doesn't matter whether a pressure switch or pedal switch is used... but the lights still weren't working. So, I buzzed all the bulbs, and they were good. I then took a pencil and used the eraser to clean the contacts down in the bulb sockets. Viola. That was the problem. So... I'm guessing the PO couldn't figure out the problem, and added the mechanical switch (which didn't solve the problem). In any case, I routed the wires back to the pressure switch and yanked out the excess wire that was running into the cab, and all is well with that. Now... on to the next electrical mystery... the green wires pictured in my OP. Any ideas on those? I'm still studying the wiring diagram, but it hasn't jumped out at me yet.

Here's a pic of the pedal switch.

This is an old thread hopefully the owner got it sorted.
The hydraulic brakelight swtches are a P.O.S. They fail internally and eventually will leak (even the replacements ).
I got tired of this so I bypassed the hydraulic switch and installed a plunger operated swich at the brake pedal lever arm. Brake switch for a 74 F100 Ford works just fine.
If the old switch is leaking remove it and install the correct threaded plug in the port.
I did not have access to a plug so I gutted my old leaking switch ,tapped it to accept a 6-32 brass screw and brazed it over to seal the screw. Port plugged.

The other wires that were dead ended may have served the Neutral Start safety switch which is supposed to only allow power to the start relay when the cluch pedal is depressed or on automatics when placed in neutral or park.

Other wires that often times can be found dead ended:
Windshield washer pump
Electric fuel fump and its safety cut out circuit
Engine compartment hood operated light switch
Front and rear running lamp harnesses will have unused connectors that side marker running lights would connect to.Lots of 1968 and 1969 trucks sold in USA are like this withonly bolt on reflectors in the locations of the optional side marker lamp housings.
Ditch the Niles fues block and get an after market fuse panel that is marketed by K4.
It is a much better piece ( covered marine grade) has room for extra circuits and uses blade type fuses.

K4
http://www.k-four.net/


Blue Sea Systems
http://www.bluesea.com/products/5026/ST ... r/featured
They are the manufacturer of the fuse block