When Good Wires Go Bad (or How I Got Stranded)

You can exhale now. The car is running fine again. Earlier this week, I reported that I'd gotten stranded 3 blocks from the house, resulting in the first time I've resorted to a tow home (even a homemade "tow" behind the SUV). I was just too tired that night to dig into the problem, but the next day it only took a few minutes to track the problem down.

You know, I am color blind. Did I mess up this spaghetti of wires while
putting things back together after recent maintenance?

I had noticed that the fuel gauge also stopped working at the same time. This almost certainly meant it was an electrical problem. I looked for other circuits that might be affected and tested the turn signal - dead too. Now I knew it was electrical. Still stranded road side I tried swapping a fuse but that didn't help. The headlights and starter motor worked, so it wasn't a dead battery. Since I don't yet have a test light or other equipment to test electrical connections in the car and I was so close to home (and it was getting cold and late) I waited to further debug and fix until I'd rested and had the warmth of the garage and better tools.

I'd recently had the Generator and Coil out for other maintenance and figured I'd done something dumb in reassembly. Rather than hunt randomly around, I took a methodical approach (after a quick check for obvious problems with the wires I'd just reconnected earlier in the week). With a wiring diagram in hand, I worked back to the common point of connection of the major circuit areas that were out. That lead me to the fuse box. I tried shorting across the fuse just in case the fuse I'd tried was broken too. No change. I got out the electrical multimeter and checked that power was making it to the input side of the fuse. Nope. The power to that point comes from the ignition switch behind the dashboard after the key is turned. I tested there - the terminals on the back go from infinite resistance to zero when the key is turned as it should, and there is 12V on the output side of the switch. That means something has gone in the wire between the switch and the fuse block.  Weird. I unhooked the wire at both ends and measured resistance.  It was a little hard to get a good hold on the connector on one side, and I found that depending on where I hooked the test lead I would get different readings.  Digging in further, I found the problem. The crimped on "quick connect" end on the wire was not electrically connected to the wire, even though it looked fine. There must have been some oxidation or corrosion. I cut off the connector with wire cutters and put a new one on. I tried to solder but the iron I had wasn't getting hot enough. I'll have to get back to that later.

The push-on connector like the one on top had failed.
Is Dielectric Grease the cure?

One thing I failed to do was squirt non-conductive "dielectric grease" into the connector before assembly. The point of the grease is it prohibits electrical flow in the air gaps, and keeps air out, so it should prevent sparking and oxidation that ruins the push on joint. I did that for a wire I'd broken off the electric tach signal wire - we'll see how it holds up. Speaking of that wire, I was heading out in the car that fateful night to pick up a new "ring terminal" to fix the signal wire that feeds the tachometer from the ignition coil to tell me engine speed (based on spark plug firing rate). That wire was flopping loose, free to ground out against the metal side of the coil. I'd figured that there would be no electricity flowing back from the gauge so there would be no problem with this. However, during the three block ride, I did notice the tach jump up from zero a few times in a way that didn't seem to match the bumping of the car. Is there a chance this caused the wire connection behind the ignition switch to fail, or was this just bizarre coincidental timing?