Last Few Electical Gremlins

Even after completely redoing the whole wiring harness for my car there were a few issues:

1. The "Charge" light on the combination gauge would come on the moment a battery was connected, it should only come on if the alternator stops producing the proper amount of voltage.
2. Brake Light sensor isn't transmitting signal properly when the brakes are on.
3. Tachometer isn't working at all and is missing all of it's internal light bulbs.
4. Fuel level sensor isn't properly sending signal
5. Oil Pressure sensor isn't properly sending signal
6. Water temperature isn't properly sending signal

So lets start delving into the issues and how I've gone about fixing them, those that are fixed.

#1 Upon further inspection of the wiring diagram wires got crossed and the wire to the light was not on the correct terminal, once it was moved and re spliced correctly battery is connected and the light doesn't come on.

#2 Brake light sensor assembly works by depressing a small diaphragm inside the screw in to transfer signal from the live wire that comes in to the wire that's attached to the brake lights. The multi-meter says it's not transferring that signal, so chances are that a new one will have to be sourced from the junkyard.

#3 I had to contact Ashcraft about this one because the previous owner had installed an MSD ignition control system, which obviously changes the way the primary circuit should be wired. According to the MSD documentation the lead to the Tachometer should come straight out of the MSD box, while the stock SAAB setup says it should go to the negative terminal of the ignition coil. Well the MSD box set-up wasn't working, and Ashcraft said that the way the VDO tach works is based off a deflection of the 12v signal coming in based off the grounding in the ignition coil. He went on to say that if the wire to terminal 1 of the tach was connected to a wire with a voltage it risks frying the tach PERMANENTLY. So with that concerning me greatly I switched back over to the stock setup. 

First impression was that the Tach isn't fried. It did react to reving and finally moved from 0 when the car started up. However the revs idle at 600, and never exceeded 2000, even when I revved the nuts off the thing. So something isn't reading correctly. So back to Ashcraft I crawled; he suggested switching to a stock style Bosch Blue Type 12 ignition coil (Most commonly know in old Volkswagens) as that's what the VDO gauge is calibrated for. German gauge only read German ignition coil, I could have probably guessed that.

#4 This is still an issue, but may be due to a broken bullet connector in the VDO specific connector, so I'll need to replace the whole thing since you can't get replacement connectors and mine is broken. It's on the list for the next trip to Nine's junkyard. If that isn't the issue the problem lays on the sender side, but I'm really only concerned with getting the electrical issues that are easiest to fix with the body off at this point.

#5 New sending unit was purchased and installed. Suspect gauge isn't working now

#6 New sending unit was purchased and installed. Gauge is suspect.