g'day I have a HJ 47 2h diesel my RPM gauge is not working any ideas where to start looking would be helpful and appreciated i've taken the floorpan off to get to the plug that comes off the Bell housing and checked it with a test light there's seems to be no power going to the sensor very rarely it will come on it's like there's a loose wire somewhere 99% of the time it's not working where should I start diagnosing from ??