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The instrument pods can be disassembled down to individual gauges. However there is a trap waiting for the uninitiated. You will notice that there is a ground wire to each pod that connects to a post on one of the instruments. There is no ground passing through the 6/8 pin connectors. So how does ground get to the various bulbs and instruments? The whole back of the pod is a 1 mm thick printed circuit board, with the copper traces facing to the rear (of the car). This distributes signals from the connector to the instruments and lights. The instrument posts are simply 4 mm threaded brass all the way down to the back of the instrument. So how does the post make reliable contact with the pc board foil? If you simply tighten down a nut on the post with the board in between, the nut will compress the relatively soft pc board material itself, which would mean as it further compresses or erodes away the current path could be interrupted. The designer solved this by leaving a 1 mm clearance in the pc board around the post, and called for a 5x4mm x 1mm-thick brass bushing to take the compressive force of the nut. The trap is that these bushings are very small and easy to lose, and will readily roll away if dropped on the floor. This is especially likely at the point where you pull the pc board off the posts if you are unaware of their presence. The speedometer pod has only three (on the posts of the fuel gauge) but the tachometer pod has maybe four times that many. As said, one of them provides a ground path for the lights and instruments, but the rest provide B+ and signals to the lights and instruments. So if you put the instrument back together with any bushings missing, the posts that don't have them may from then on have no or intermittent connectivity. This is especially pernicious in case of the one that provides a ground path because that being missing causes the indicator lights to act very oddly.

The solution to this is to make sure the pod is facing down when you pull the board of its back, and to watch carefully in case any bushings come away with it. If you do lose one or more, you can make a substitute from a short piece of 1mm copper wires formed into a 5 mm OD "donut" fitting very tightly around the post. 18 gauge solid (not stranded) copper wire is slightly over 1 mm in diameter.

Why would you want to disassemble an instrument pod? Two reasons I can think of:
  1. To replace an individual instrument that has failed.
  2. To clean off the foggy residue on the clear plastic that builds up after 50 years.
  3. To debug a pod that is not working correctly for some other reason (perhaps a missing bushing).
Mystery: why did the designer not just allocate one more connector pin for ground?
 
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