trying to get tach to work

[seanman]

alright guys, ive been driving my sr for about a year now and the tach has never worked. I've been told that the tach from the pignose years wont work with the sr. So i tried switching out the whole HUD to the jdm one that came with my front clip, still the tach didn't read. I pretty much gave up but i want so badly for my tach to work. so i started working on it today. i checked all my wiring which i did according to frsport, everything looked good except the fact that when i was looking at my fsm to test the tach and what not, it says first check from terminal 21 to ground and you should have battery...mine didn't and the wire coming out of that terminal is green and not connected to anything which frsport said i wouldn't use but the fsm is telling me i should be getting continuity. So moved on to the next step which is check for a voltage output with the engine on between terminals 12 and 22, so i did and i got a voltage that changed with throttle position which is good. Also it says that the tach is regulated by a signal from terminal 7 to combination meter terminal 12 for the tachometer...i dont understand fully what that means

[seanman]

anyone? tach issues!