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This critter is a speedometer from a 1990 Porsche 964. I call these "hybrid" speedos because while they are ELECTRIC [not cable driven], they still retain the mechanical
odometer registers.
The usual problem with these speedos is the break-up of a couple of wee little odometer drive gears that were shit quality to begin with. Of course, you have to
take these things all apart to get to those little gears. On the left, above, is the
speedometer assembly, with its printed circuit board. In the middle, a plastic gasket, and on the right, the outer, steel, "can" or housing. The outer rings and the [plastic]
glass have already been removed. [Uhhh...PLASTIC glass? In a Porsche? Oh my...]
Here the printed circuit board has been separated from the main frame of the speedometer. We still are no where near the busted-up wee gears, but we're
gaining on it...
Believe it or not, this mish-mash is a little pancake motor that drives just the speed needle. It is fed by a little sensor somewhere in the bowels of the car, driven off the
final drive of the transmission. And...of course, there is another little motor that drives the odometer gears. And, assuming you can find THAT motor, you'll find the little busted drive gears jammed in behind it. Keep looking...
See, when the crappy little gears shredded, they sent little gear bits all through the
rest of the speedo. You have to take the bloody speedo all apart--usually--in order
to use dentist's torture tools to dig out all the little gear parts. If you don't, those
broken up parts will sure as hell screw up the new gears you install. Fun stuff....
Here is the reconditioned, CLEANED-UP, speedometer, WITH new wee gears. The
new gears are made of a different, high quality material that will probably outlast
the rest of the speedo. They will certainly outlast the [plastic] "glass"........HA!
It has been Porsche instrument reconditioning time around here for a while. Above is a typical Porsche 911/912 multi-gauge unit, taken apart, cleaned, gauges tested and OK, and ready to go back together.
This is a typical before and after picture. The temp gauge unit on the left is pretty much what they look like when I get 'em. The multi-gauge unit on the right is what they look like when I'm done working my magic on 'em.
Here are two pages [of six] that I did on the first 912 speedometer I reconditioned. I make these illustrated how-to notes for ME on EVERY different instrument I get in for reconditioning. Keeps me from having to re-create the wheel the next time I get this type unit in. My speedometer rebuild "notes book" is well over 100 pages long at this point...
I believe in TEST SET-UPS for nearly everything I recondition. This is a set-up to test a VDO tachometer. Four cylinder VDO electric tachs indicate TWICE the RPM of the input. So if I set the drill at 1000 rpm, the tach better read 2000. This tach, from a Porsche 912, DID read correctly. Note that I tested it before I disassembled it for reconditioning. It looked pretty nasty and had obviously seen better days.
All five reconditioned units, ready for another 51,596 miles in a Porsche 912. Even the average egocentric Porsche owner would love 'em! HA!
