Well, I'm still working on this. I had really hoped to have something finished before I updated the thread but electrical stuff was kicking my butt and know I'm have the first difficulties with getting the truck running that I've ever had. This might be a long post just because I ended up all over the place on things I was working on.
The goal was to get the instrument cluster working, the radiator fan working, and possibly relay the headlights. I started with the odometer. Pretty simple, the gear gets brittle and breaks, normally when someone presses the trip button while the truck is moving.
I didn't take any useful pictures of the old gear or the new gear installed but the shaft the gear is supposed to be on is above my thumb. Fairly simple. Just pressing the gear on without breaking any other pieces of brittle plastic.
Next, I attempted to get the fuel gauge to work. The fuel gauge hasn't worked since I bought the truck and the water temp gauge is intermittent. Typically, this results from a bad voltage stabilizer.
The back of the instrument cluster with the mylar circuits.
The three pin voltage stabilizer. I already had replaced it and it seems to be working properly. It has ground, power, and outputs 10V.
I'm realizing now that I don't have any pictures of my attempted solution but basically I back fed the gauges. I connected a wire directly from the 10V output to the gauges, a wire from power to the power input on the voltage stabilizer, and a wire directly from ground to the voltage stabilizer.
Finally, I want to get the radiator fan working. After taking way too much time I found out that it was just the relay. As far as I can tell the Bosche relays for these are no longer made. I just bought a generic four pin relay with the same ratings.
You can see in the second picture how much corrosion is on the old relay. The water that got on the fuse box is likely going to continue to haunt me. After replacing the relay, the fan turns on when the thermoswitch is bypassed. So... success?
I wanted to see if the thermoswitch was working and check the odometer so I figured I would take the truck to end of the road and back. It wouldn't start. Turning over slow. There seems to be a parasitic draw to the battery. I tried jump it. Still not starting. More out of frustration than having a good reason, I decided I would check the glow plugs. I haven't looked at them yet. Tried to loosen the nut holding the bus bar to the first plug... and broke the stud off the plug. You may be catching on now. I break things. A lot.
As you can see, I ended up breaking the stud off all but one of them. So, that resulted in my purchasing new glow plugs. I had also been considering a reasonably well documented upgrade to the glow plug wiring. I figured now was the time to give it a try.
The new glow plugs.
Removing and installing these things is a pain. You can see the screwdriver I'm using to push the plug into the hole and the ratcheting wrench that I can get about 1/8 of a turn at a time with.
You can kind of see the new plugs installed.
Next was the wiring. The original circuit has all the glow plugs on one wire with one 60 amp fuse. The upgrade is to run the glow plug signal to a lawn mower starter solenoid that then sends battery power to a fuse box. Each glow plug then has its own wire with a 20 amp fuse. In the picture above, you can see where the 60 amp fuse should be but both the signal wire and the wire to the plugs were just on the same screw.
Conveniently, my fuse box fit the same exact holes as the old in line fuse.
For the wires from the fuse box to the glow plugs, I cut the ring terminals so that the wires can be removed from the plugs without removing the nut holding the wire to the plug.
Once again, hard to see but the wires installed on the glow plugs.
The fuse box and starter solenoid wired.
The glow plug wiring as it sits in the engine bay now.
So, with that done, I also installed new battery cables which is frequently recommended for Mk1 Rabbits. Then I tried start the truck again. It turns over much faster now. Whether that's the new battery cables or the glow plugs, I'm not sure. It still won't start. There's power to the glow plugs. The starter solenoid is kind of loud. It still won't start. Turns over long enough that I'm worried about the start. I popped the fuel lines loose from the injectors and turned it over... no fuel. Well, that's something. I replaced the fuel filter, which I should have done a long time ago. The old filter had quite a bit of water in it which was concerning. Turned the engine over several times and eventually fuel came out of the lines. Connected the fuel lines. Tried start the truck again. It kicked once and soot came out of the exhaust and still wouldn't start. Disconnected the fuel lines and turned it over. No fuel again. This is frustrating. Sometimes I can see bubbles in the fuel line going into the injection pump and it appears there is fuel there. That leaves two options. The stop solenoid has power but I haven't checked if it operates. That could be the problem. Or the injection pump could need a rebuild... That would be rough. Its not impossible that debris in the fuel tank has clogged the in-tank filter or the main fuel line but that seems unlikely because there is fuel at the pump. I'll check the stop solenoid first. Then probably the in-tank filter. I can check the fuel sender while I'm at it. After that, a pump rebuild might be needed.
So that's where I'm at. I did manage to find another dash for $20.
I think I might take bonylad's suggestion and try flocking this one although its almost too nice to change compared to the minimal experiance I've had with Rabbit dashes.