Hi guys. Just finished rewiring my car and amongst other things I fitted a safety switch used in LPG setups. The tacho signal is being directly received from a Crane Hi-6 unit (green wire) then on to the Tacho. The Tacho works but the safety switch is not being activated. Any clue as to why? I've had to temporarily bypass it to get the fuel pump working.

Did you use all the pins??

Is it new?

Did the light come on with the ignition?

Yes to all. I've heard there's something about the sine wave signal or something

Apparently the signal reqiured is a swuare signal, and it usually operates off the negative side of the coil. The tacho output by the Hi-6 does this so unsure of why its not working. Its a straight wire from the Hi-6 to the relay.