K75 - Problematic Speedometer, Odometer, and Turn Signals

[december454]

Howdy there, wanted to give a quick update on this thread.

I replaced the LM-2904N op amp which amplifies the signal from the speed sensor. No dice, unfortunately. The speedo / trip meter are still inoperable. Also, there was a faint smell of burnt electronics when I cracked open the gauges; I do not recall this when I first worked on the gauges during my road trip.

I'm going to throw in the towel and pick up a used gauge cluster on eBay. If anyone with a bit more electronics prowess wants my problematic gauge cluster, PM me, and I can ship them your way. (within the U.S.)

Take care.

[daveson]

Let's say there's a problem with the blue/green wire, that might cause the Speedo to stop working. The fact that the auto cancel feature works intermittently, adds weight to this as a possibility, I think. How likely is it that this is the problem? Dunno, I'll say somewhere between 0% and 100%, but it's such an easy thing to do, it's worth checking before ordering a new cluster.

Let's say there's a short in this wire, when you install another instrument cluster, that might also end up with a burnt electronics smell. There's continuity between the ends of that wire, but that doesn't eliminate the possibility of a short.

I would unplug the flasher unit and isolate the blue/green wire from the instrument cluster to see if the Speedo then works. A quick way to isolate it from the instrument cluster is to fold a piece of paper, longer than it needs to be, and push it into the socket for the green/blue wire pin. Longer than it needs to be, so that it's easy to remove after this test.