One possibility: If the voltage drop and the discharge spike are with the key turned on into the "run" position, but the engine not started, are there are clicks or clacks at the beginning or end of the discharge (or both)? If so, it may be due to the controller for the glow plugs cycling normally. There would be a discharge as a solenoid applied current to the heaters in each cylinder, and then the discharge would stop during any pauses in a timed cycle. The timing I have experienced is usually slower than in the video, but it's not impossible that is what the discharge is.
As far as flashing lights, I don't know from experience, but I have seen ads online for replacement International instrument cluster circuit boards. I am assuming a high percentage of them become intermittent or go bad. If you suspect the circuit board might be the problem, and not wiring or sensors, I would first unplug and clean both sides of all the harness connectors with a pencil eraser. If I really got serious, and did not want to buy a new board, I would pull the instrument panel apart and use a magnifying glass to look for hairline cracks in the printed circuit runs. Again, I don't know if that is the problem with these, but I have had to repair PC boards that developed cracks in other equipment in the past. If you have cracks, you need to decide if you would repair or replace the board.
The field fix for a hairline circuit board crack is to:
- gently scrape away a little bit of any lacquer or other protection a very short distance on either side of the crack, until you have some shiny metal on both sides.
- apply rosin-core electronic solder to the circuit trace on both sides of the crack with a pencil soldering iron, heating gently just until the solder flows on the bare metal. (Solder is not glue - it must bond with the metal - if you just have a ball of solder sitting on top of the metal, it is a bad connection.) Don't leave the iron on longer than necessary, too much heat will cause the circuit traces to pull away from the board, and you will need to repair a longer section (ask me how I know).
- lay a few strands of wire across the crack, and re-heat each side adding a little more solder so the wire sinks into the solder previously applied, and the solder flows on the wire strands as well. On wider runs, "solder wick" flat metal braid works very well, but you must flow solder throughout the weave before touching it to the board, and it must be held down with a probe when removing the iron.
- do not allow anything to move once you remove the pencil iron and allow it to cool. The wire or wick may want to stick to the iron and not the board. You can hold pieces in place with a needle probe, and blowing gently on the connection will speed its cooling.
If you get too much solder on the repair, there are several ways to remove it. Clean off the soldering tip with a wet sponge, the "bare" tip will pull a small amount of the solder back. Turn the board over while the solder is flowing, and give it a quick tap to drop some excess solder on the workbench. This usually results in thin nickel-sized splashes, that can easily be peeled up without damage unless you splash them onto a plastic surface. If you have solder wick, touch it against the connection, and then heat the braid so it sucks the solder up into the weave. Or use a suction tool designed to 'vacuum' the solder off of the board. The spring-loaded ones are handier than the rubber bulb models, though there are expensive ones with electric pumps, too.
