More Bad Wiring...

[ckuske]

Hi All,

I helped a neighbor haul something in my neighborhood with my truck.  I pulled it back in and while it was idling, I popped the hood to just look for anything odd.  I noticed a spark down by the passenger exhaust manifold.  Not good!  At first I thought it might be arcing of the spark plug wires, but it was a dangling wire that had touched the manifold, and the insulation burned off and was causing the spark.  I was pulling things together into a bundle to be kept away from the manifold in the future, and following the wires, I noticed something more concerning:



This goes to the A/C compressor.  I looked in the EVTM and see a diode there in the A/C section, but there is no blue wire that I can see.  As you can see, the wire other end of the diode isn't connected to anything!  I will try to look again, but does anyone have any experience with this circuit and can tell me where this diode goes?

Looks like I need to replace this whole area too, splices and all.

[ckuske]

Here is a "better"(?) picture.  The wire going to the diode is odd - blue with yellow hashes on one side of the same length of wire, and black with yellow hashes if you rotate the wire.



I know this is the circuit, but I'm having a hard time understanding where the diode is supposed to go based on the wires in front of me...

[Gary Lewis]

Chris - I'm not sure I understand the question.  But forgetting about wire colors, the diode should go across the A/C compressor's coil, with the cathode being on the plus side and the anode to ground.  That shorts the back EMF off the coil to ground when the clutch is released.  Without the diode that energy is sent into the truck's electrical system.

But I've never seen a wire in a Ford with two different markings: "blue with yellow hashes on one side of the same length of wire, and black with yellow hashes if you rotate the wire".  So I can see how you are confused - I am as well.

It doesn't feel like I answered the question(s), so try me again?

[ckuske]

Well let's ignore the weird color wire - I don't know how to explain it either.  Maybe over time the insulation got some other wire color transferred onto it.  It is weird that the true base color of the wire is blue, turn the wire over, and the other side is black.  Same yellow hashes on both sides.  I scrubbed the wire with a toothbrush and Dawn, and nothing besides gunk came off.  

Keep in mind I am a software guy, not an EE   so I am willing to ask a dumb question here...

I have a diode with one end connected to nothing.  Are you saying I should be splicing that diode lead into the black wire (wire 57 in the EVTM diagram above) that then connects to the A/C compressor?  The black wire I'm referring to is the bottom wire in my second picture.

[ckuske]

I went back out to the truck and answered my own question (I think)

The black wire with no hashes has a section where you can tell there was a wire spliced/swaged onto it.  I'm pretty sure that's where the other end of the diode went and it matches up to your description.

If you could confirm though, that'd be great!  I should have thought about it a little more myself first, but I was upset to see more junky wiring!  The diode wire must have gotten ripped off the splice when I got the A/C redone and the guy didn't notice, then I didn't!

I'm also double checking my wire routing to make sure I don't melt anything else... there's just so much of everything in my engine bay.  I'm jealous of these clean I6 setups with like 8 wires total and a couple vacuum lines. And then there's MY engine bay.

[Gary Lewis]

Yes, I think you answered your own question.  That black wire goes to ground and if it was spliced into that you'd be good.

As for engine bays, look at Big Blue's.  It is CRAMMED!

[ckuske]

Thanks, I cut out that nasty section, and soldered everything back together, put shrink tubing around it, etc.  It should hold up much better!

And yes after looking at Big Blue, I feel better!  But not in a negative way towards Big Blue mind you, there is just a lot going on due to all the goodies!