Chasing the Hapy Electrical Gremlins (part 6)

Continuing the saga of fixing the front-to-back (or original bus to donor engine) wiring, today I will cover some of the bus install joy. Consider that the positive battery cable has been disconnected this whole time, and the battery has been on a float-charger. I strongly suggest that you do the same any time you are playing with your electrical system.

Make It Fit

how it looked before

When I left off last time, I had accidentally cut wires from the donor fusebox that I ideally would not have. This led to a complete re-do of the fuse-box wiring harness. After spending my holiday break addressing that harness, and test fitting, I was about ready to start installing it. I plastic-wrapped the clumps of wires, and took the whole thing out to Hapy. I spent a few minutes looking at how things would fit and it quickly became apparent that I could have shortened the wire-clump going to the oval T10 by a couple of feet. Oh well. I stuffed the T10's, the custom T12 and the collection of leftover wires down through the hole in the bottom of my spare tire well. I should probably point out that when I first did this conversion 10 years ago, I cut a larger hole down there, approximately 1 inch across by 2 inches front-to-back.

With the harness pretty much where it needed to be, I removed the dash pod from it's mount and plugged in the blue and green connectors. The dashpod set back into place, and was bolted back in quickly, like end-to-end in 15 minutes. Next, I plugged in the computer and pressed it into place on the plastic holder/stand. The ECU really didn't move much once I had it set in, which, when we consider the thickness of the cables heading into it, really doesn't surprise. I will be applying bungy-ties eventually to hold it in place. This left the fusebox. I test fit it to make sure the wiring lengths were good and then let it sit so I could finish the wiring of the glow-plug relay.

Last Few Wires

how it looks now

During the harness rewire work, I left the glow-plug relay and related heavy wiring in the bus. I had cut the trigger wires (label-label-cut), but the hotwire supply and to-the-glow-plug wires were left alone believing that splicing wires that thick should be minimized. So, I had to re-integrate that circuit. The wires were clearly labeled, and long enough so the splicing was easy, and the relay holder clicked right into it's designated slot. All that remained above deck was tying down the ground ring terminal from the larger ECU plug; I leveraged the fusebox mounting screw after confirming it was a solid ground. The final result is pictured on the right here. Considering what it used to look like (top picture), it is hard to imagine these are actual before-after pictures.

Next, I moved down into the engine compartment. It was an unruly mess (see bottom picture). I had shoved the harness through the hole, and left everything else as it was. My first steps were to plot out where the various wires would go, and that started with the always-hot lines for the 2 donor relays (109, 180). The 180 supply line was a hideous hack I did when I had no money, but it worked. I have more resources now, but more importantly, I have a long enough wire of the right size. Once I determined how long a run I needed so the wires could run along the top of the engine compartment straight back from the spare tire well, turn 90* over the top of the engine hatch to the battery with some flex in the wires, I spliced in wires with ring terminals for the battery-top fuse box. Next, I moved to the remaining little wires for things like the alternator "D" signal and the coolant level.

wiring T12 to cable

A few of these little wires needed to be extended. I re-routed the coolant level 2-wire cable. It had previously run along the front of the engine. Now, it runs along the top of the engine compartment hatch like the rest of the signal wires from the engine. I wrapped the little wires into another plastic wrap, and tucked the cable into the wire loom holder along the top of the engine compartment over the hatch. I followed that with the power supply wires. Finally, I plugged in all of the T10's, the T12 and the 2-wire glow-plug harness. Believing everything was set, I removed the float charger, and started testing amp draws from the battery post to the battery connector. The draw could be measured in milli-amps, so I figured it was safe to put the battery cable on the battery and see where smoke came out. I'm kidding; with the care I took for the wiring, and the fact that 95% of the changes I made were on that one harness, everything should be fine. The only changes I made that were not on that harness were the always-hot supply lines and tying signals from the rear to the front for things like a low coolant light.

Of Course It Didn't Work

below deck unruly mess

Feeling relatively confident, I put the battery cable on the post. No clicking, no other noise. So far so good. Interesting... the dash-pod was not showing the odometer like it used to. Slightly puzzled, I went to turn the key to run. The starter tried to spin, so I knew I had something wrong. I pulled the starter relay, and tried again. This time, I heard a slight pop noise, and the battery discharged. Clearly something, or many somethings, are wrong. Neat.

Well, that's it for today. I am sure I will figure out what I did wrong, and I hope it will be a minor, simple thing. The wiring was well labelled, and the other modifications I made were small. I can tell you that I pulled the diode between the start signal and the run signal. I've decided that if I need to keep that, I will move it to the ignition switch and out of the fuse box. I will keep posting on my progress until I figure out what's wrong. I don't think it will take many hours of labor, but finding the time for those hours is the challenge. Thanks, as always, for following along-