Cannot get a tach to work

[Italian_Tuneup]

Running into a wall on this now. I have a Dakota Digital signal converter installed on the M60 swap. I cannot get any of the tachs I have to register. The cluster that came with the car worked when I got it, but then it sat for 2 years. I read the SI board batteries can go bad so I took it apart. Batteries badly corrided, broke a connector trying to get them undone. So I put the "new" cluster in that I had bought that had a 7000 rpm tach rather than the eta tach. That one wouldn't work. So I took it apart. Same issue, corroded batteries. So I got ahold of Bavarian Restoration to get them rebuilt into one. They said don't waste your money, get a new style cluster. So I did. Just installed it, still no tach. This is out of a M42 car, so I completely took the Dakota Digital unit out of the equation and just hooked the tach signal off the ECM to the wire going to the cluster, figuring it will just read double. NOTHING. I have checked continuity, I have verified the pins, I have checked resistance. Nothing is out of line. The Dakota Digital unit flashes that it is detecting a tach signal from the ECM. So WTF is wrong here? I don't have any wires hooked up to the "Green" connector on the cluster, because it was only 1 wire, and I can't figure out which of the multitude of pins it should go on, or which wire it even was for that matter.

Any advice? I was really thinking the Dakota unit was junk, until hooking it direct to the signal from the ECM did nothing. Getting beyond frustrated with this situation.

[JGood]

You directly connected pin 47 of the DME, to pin 7 of the blue C1 cluster connector, and have no tach movement while revving the engine?

You have the other connectors on the cluster hooked up? Are the other gauges and lights functioning?

[Italian_Tuneup]

Yes, Pin 47 output to pin 7 on the C1. No tach response. Everything else hooked up, all fuses good. Well, the green connector is not hooked up because I don't know what wire or what pin goes to that but I was told that's only for the 02 sensor counter? Fuel gauge works. SI lights come on, one flashed furiously. Not sure if thats normal. Not sure if the temp gauge worked, I didn't want to try and undo the connector and ground it. Tach did not do anything. Only thing it does is blip up to about 500 rpm about 2 seconds after key off. The SI batteries might be bad. Took the board to Tacoma Speedometer to get the batteries replaced. Super frustrated with this. It's a horrible design. If replacing the batteries doesn't fix this, I think I am going to have to go aftermarket, even though it will look like dog shit.

[JGood]

The green connector on the back of the cluster is a vehicle speed output. It's used for cruise control on stock e30's. I used mine for VSS input to the m60 DME. All the pins on that green connector are the same... pick whichever you want. You can prove this by doing a continuity test across any of the pins.

[Italian_Tuneup]

The green connector on the back of the cluster is a vehicle speed output. It's used for cruise control on stock e30's. I used mine for VSS input to the m60 DME. All the pins on that green connector are the same... pick whichever you want. You can prove this by doing a continuity test across any of the pins.

Oh, good to know. Thank you. I stole my VSS signal out of the loom running to the 13b OBC since I am ditching it for a euro clock since it was junk.

[Italian_Tuneup]

Update to this, I spent the past month going back and doing more color sanding on my paint. Got the SI board back from Tacoma Speedometer and finally put the cluster back together today to test fire it while I re-bled the cooling system again. Same story, no tach response. Dakota Digital unit is supposed to send a 2000 RPM signal when messing with it, but it would just make the needle blip. BUT, if I hook the tach-out from the DME direct to the tach, bypassing the DD unit, it now reads 2x like it should. So now I know the tach and my wiring is good. Hoping this hasn't been a junk Dakota Digital unit all along, but I doubt it since the direct-to-tach issue didn't work the time before. Still think this is a shitty design!

[JGood]

Sounds like the SI board was causing the issue, and now you just need to get the DD set up. Check the power, ground, and set the DIP switches. There are troubleshooting lights on it as well. I'm not sure what you mean by "Dakota Digital unit is supposed to send a 2000 RPM signal when messing with it"

I literally plugged mine in and had it working in 30 seconds, and it's been fine ever since, haven't touched it in 8 years.. You're just experiencing a string of compounding issues I believe.

[Italian_Tuneup]

So the issue with the converter appeared to be my interpretation of the ETM. To me it appeared the tach was using 12v circuitry so I set up the DD unit on HIGH output. Talked to DD tech support, they had me test output voltages on the unit which were good, so for the heck of it I switched it back to LOW and hooked it back up. Tach works perfectly now.

Time to finish buffing and polishing, get the glass back in this thing and start shaking it down!