Tacho issue / Laurel C35 Swap / RB20DET

[madnjpn]

Hi guys, got Nissan Laurel C35 some time ago, it was manual swapped and also engine swapped with RB20DET from R32, initially it had RB20DE.
The issue is, I cannot get tachometer to work, the car is year 2001 and I think that facelift got different half/digital cluster.
I am getting tacho signal from ECU on pin 7 (red/yellow) , but tachometer wire from cluster itself gives out 8v (yellow/violet) So I guess it expects 12v signal. I tried adding 10k + 12v IGN bridge method but still nothing... Anything else I can do before I buy signal converter? I dont even know which one to get. Thanks

[VStar650CL]

The 8V from the gauge indicates it already has an internal pullup resistor, so it probably wants an open-collector signal (the ECU grounds the wire but doesn't "push" any voltage). However, it also may want a high voltage signal if it originally connected to the coil and not an ECU. Nissan used a mix of both types in the 90's, so without a wiring diagram it's a crap-shoot. It also may not be responding because the number of pulses-per-rev from your ECU may be way lower than the cluster expects. To test it out, I'd start by spending $10 on something like this:
https://www.ebay.com/itm/386169756730

It's a PWM tester, but by setting the duty to 50% and varying the frequency, you can see if there's a signal speed that gives you a response. If so, a little math will tell you how much you need to adjust the signal. You may be able to do that with a tune or you may need a tach converter. The cheap China PWM testers all have open-collector drive, so it can also tell you if that's a problem. If the tach still doesn't respond then it probably wants high voltage, so you'll want to try a booster and not a converter. I can make some suggestions about what you need depending on what the tester tells you.