tach troubles

i bought a timex tachometer and those frigging ppl didnt send any instruccions with it

i found the wire and hook it up, now the rpm goes too high

as an example in idle reads 3,000 rpm and when i go at 65 mph

it reads that i go at 10,000 rpm

i moved the switch and nothing

i saw a post saying using an adapter, do i need an adapter for that

tach? or tach is faulty? ( btw i used the yellow wire not the pink cause pink didnt do a change on tach, only the yellow wire moved the gauge

thanks ppl, and im sorry for keep asking about tachs i know there r so many post about them

but im in troubles hope u can help :disappoin

Next time buy autometer.