Wiring the Fuel Pressure Switch to the Hobbs Hour Meter

[Angela]

Preface - I'm not a DC wiring guru and if you throw a switch in there, I'm a little more useless. I am, however, pretty good at replicating what was there which has worked well for me over the years. I understand AC wiring way better.

That said, I need some help with reconnecting the wires that go to my fuel pressure switch which runs the hour meters. My hour meters have never worked since I got the boat and I want to get them working again. So, I'm taking advantage of working on that in conjunction with upgrading the secondary fuel filter system - one of this "while you're in there" things - and that's were I find myself replacing the pressure switches located at the secondary fuel filter.

The port engine has been rebuilt, or partially rebuilt, back in 2000 (before I owned her - something about replacing a cam shaft, I think - I'm not going to go look it up now), and the starboard engine is original and not nearly a pretty as the port. I'm working on the ugly starboard engine. I bought a new fuel pressure switch (the old one fell apart in my hands) in the hopes that perhaps it was bad (I'm sure it was) and that's why the hour meter doesn't work (no clue if that's the reason). I also installed a new slow blow fuse for that meter, just because I have a bunch on hand and it can't hurt.

In reconnecting the wires that go to the old switch, I took note of how it was wired. Just for grins, I looked over at the port engine to confirm and found that these switches were wired differently between the two engines. Neither meter worked, though.

The switch has three connections, NC, NO and C, normally closed, normally open and common, I suppose.

The starboard (the one I'm working on) was wired with the red/black tracer wire attached to the C and red/white tracer wire attached to the NO; nothing on NC.

The port is wired with the red/black tracer wire to NC and the red/white tracer wire to the NO; nothing on C.

Long story short - what is the proper way to wire this switch? Obviously, I can't go by what's there since they are different and neither meter has worked anyway. I don't know the harm if I hook them up wrong either, so I'm asking for some help.

Thanks!

 

[dsharp]

All the switch is doing is completing the circuit. Do you have a picture of the back of the hour meter? If it has a hot wire going to it then the switch is completing the ground circuit. One wire goes to normally open. When you have fuel pressure and it "closes" and lets the current travel to the "c" terminal. From the "c" terminal it normally goes to ground. That's why we need to look at the hour meter. You can use the switch to complete the negative path or the positive path. See if they're taking power from the "b" terminal on the key switch.There should be a + power source, or red wire going to the hour meter. From the hour meter there should be a - negative wire that goes to the nc terminal on the hobbs switch. Then run a wire from the "c" terminal to a ground lug on the engine block. Honeywell's website said that you won't hurt the meter if you get your wires crossed up. I don't understand the wire colors that you have now. That's pretty common for previous owner's to use whatever wire that they have on hand. That sounds like wire that came with a piece of electronic equipment. A 16 or 18 gauge wire should be heavy enough.I hope I didn't make this more confusing.