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Bad Tachometer - looking for replacement (KZJ78)

kgrove

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May 3, 2021
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I'm pretty sure I've got a bad tachometer on my KZJ78. Originally it was stuck at 1000rpm even when the car was off, so I did some investigating. After pulling the instrument cluster and removing the tachometer unit, it appears one of the coiled copper springs is bent. I'll attach a photo at the end as maybe somebody has seen the inside of one of these and confirm as the diagnosis is difficult without having a working tachometer available for visual comparison. In the photo you'll see two coiled copper springs on either side of a white plastic disk, all on a spindle that moves the needle. One of the springs is parallel with the photo point of view, so all you see is the side, but the upper spring is at an angle so you can see the coils. The upper spring (at an angle) rubs and makes noise as the tach needle is manually moved, which is part of why I'm confident the spring is bent. A few items or questions:

1) Have any of you opened this tachometer or a similar tachometer to confirm that these two coil springs should indeed be parallel and that therefore my tach is physically broken and needs to be repaired or replaced?
2) The part number I think is 83242-6A100 (83242-6A120 is also listed, but I *think* that is the one for the Prado's with the rear diff locker that have additional indicator lights for differential operation... I've been unable to find a photo of either part number to confirm). I've struck out on all sources in trying to buy a new part.... Megazip, Partsouq both list it as discontinued. Amayama said it was in stock, but as usual with rare parts, they notified me a week after ordering that it was unavailable. I've also tried a couple used parts suppliers in Japan and have so far found nothing. I've even expanded my search to include the whole instrument cluster as I can always take the tachometer and use the rest of the cluster for future light bulbs etc. Anyone have any other ideas to source either new or used parts? Since the Prado was never sold in the US, my view of used parts suppliers is much more limited.
3) other than finding a new part (which is beginning to seem very unlikely) or a used part supplier, any ideas how I could get this repaired? I've self-taught myself a few electrical skills, but this one seems far more delicate than I'm probably capable of myself, and I'm not even sure who I could ask for help, especially given I don't even have details on how it's supposed to work (e.g., signal profiles so the could test if a repair is working or the nature of the failure). Who or where works on these kind of electronics? I can't be the first guy that's had to deal with instrumentation problems like this.

If it helps circumvent a few questions or suggestions, I have no idea how or when this broke. I bought the car at a Japanese auction a few months ago and this was an undisclosed problem on arrival. There are no other electrical or instrument cluster problems that I'm aware of. That said, there was a broken piece of plastic on the dash just below and to the left of the instrument cluster, so perhaps there was some kind of physical impact to the dash that bent that spring... impossible for me to guess what a prior owner may have done with the car.

I appreciate any help anyone can throw out here. I'm continuing to scrub the internet looking for used parts or a new part supplier who happens to have one of these tucked deep in their warehouse. My worst case scenario is I put the broken tach back in the dash so I at least get to use it's "check engine" warning light.


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