tach issue

[rb250sx]

On my series II rb25 ive wired up the tach, signal from my PFC is good, at idle it is about 7.some volts or so. checked it at the plug for my cluster and signal is still good. so i checked the ground and the ignition voltage at the plug and both are good as well. I started by plugging in my stock 240 cluster and no movement from the tach. So i tried hard wiring the 3 pins and still nothing. So obviously i thought my tach could be bad, but i have 2 other tachs that i hard wired, one from another 240 and the rb tach. Same thing, no movement from the needle at all. My stock tach worked fine before the swap, and the possibility of all 3 tachs being bad seems pretty strange, so what else am i missing here?